Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Basic Electronics

Basic Electronics

Raghav G Jha

May 01, 2006
Tweet

More Decks by Raghav G Jha

Other Decks in Science

Transcript

  1. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 1
    Basic Electronics
    Basic Electronics
    “Hundred years ago,
    no body knew electronics;
    Today, everybody knows it.”

    View full-size slide

  2. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 2
    Basic Electronics
    History:
    Thermionic emission was observed by
    Thomas Alva Edison in 1883.
    In 1904, John Embrose Fleming invented
    Valve. Lee Dee Forest added another
    electrode & named it Triode in 1906.
    Transistor was invented by William
    Shockley, Bardeen & Brattain in 1947.
    Jack Kilby invented IC in 1958.

    View full-size slide

  3. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 3
    Basic Electronics
    Fundamentals

    View full-size slide

  4. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 4
    Basic Electronics
    Matter:
    Anything that has mass and occupies
    space.
    Matter is found in 3 states.
    1. Solids
    2. Liquids &
    3. Gases.

    View full-size slide

  5. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 5
    Basic Electronics
    Substance means any solid, liquid or gas.
    In Solids:
    1. Molecules are quite close.
    2. It has definite shape & volume.

    View full-size slide

  6. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 6
    Basic Electronics
    In Liquids:
    1. Molecules are relatively at more
    distances.
    2. Definite volume but no definite shape.
    In Gases:
    1. Molecules are at very large distance
    compared to their size.
    2. Neither definite volume nor shape.

    View full-size slide

  7. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 7
    Basic Electronics
    Matter is composed of small particles
    called Molecules.
    Molecules have free existence.
    A molecule can be further divided into
    smaller particles called atoms.
    According to modern theory, the basic
    constituent of all the matters, whether
    elements or compounds, is an atom.

    View full-size slide

  8. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 8
    Basic Electronics
    The electrons may be emitted from an atom
    by any one of the following methods.
    1. Thermionic emission.
    2. Field emission.
    3. Secondary emission
    4. Photo emission &
    5. Radio active.

    View full-size slide

  9. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 9
    Basic Electronics
    What is electronics?
    The branch of physics that deals with the
    emission and effects of electrons and with
    the use of electronic devices.
    What is emission?
    The release or discharge of an electron
    from its parent atom.

    View full-size slide

  10. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 10
    Basic Electronics
    Structure of an atom?
    1. An atom consists of a central part called
    nucleus.
    2. There are protons and neutrons in side
    the nucleus.
    3. In the space around nucleus, electrons
    revolve in circular or elliptical orbit.

    View full-size slide

  11. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 11
    Basic Electronics
    The atom is believed
    to consist of central
    nucleus surrounded
    by orbiting electrons.

    View full-size slide

  12. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 12
    Basic Electronics
    Unit positive charged is called protons.
    1. It has a charge of 1.6 x 10-19 Coulombs.
    2. All protons obtained from different
    elements are quite identical.
    3. Protons rest in the nucleus and they do
    not move at all.
    4. The mass of a proton is 1845 times that
    of the mass of an electron.

    View full-size slide

  13. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 13
    Basic Electronics
    Neutrons:
    1. It is electrically neutral.
    2. Neutrons rest in the nucleus and they
    also do not move at all.
    3. Its mass is almost equal to that of
    protons.
    4. All neutrons obtained from different
    elements are quite identical.

    View full-size slide

  14. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 14
    Basic Electronics
    Electrons have two different motions.
    One is orbital motion due to which they
    revolve around the nucleus.
    The second one is spin motion due to
    which they rotate at their own axis like a
    top.
    The same way as earth rotates. Think how
    day & year changes?

    View full-size slide

  15. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 15
    Basic Electronics
    Laws governing atomic structure:
    1. A normal atom is electrically neutral.
    Therefore, No. of electrons = No. of
    protons. It is so because of equal
    magnitude of charge in an electron and
    a proton.
    2. The number of electrons or protons
    present in an atom is known as Atomic
    Number of the element. For example:
    Cu-29, C-6, Ge-32 etc.

    View full-size slide

  16. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 16
    Basic Electronics
    3. The atomic mass or atomic weight of an
    element is a number, which is equal to
    the sum of protons and neutrons present
    in one atom of that element.
    4. The distribution of electrons in different
    orbits is governed by the rule 2n2, where
    n is the number of orbit. Thus the
    maximum number of electrons in K, L, M,
    N, O, P, Q orbits are 2, 8, 18, 18, 8, 2
    respectively.

    View full-size slide

  17. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 17
    Basic Electronics
    5. For starting a new orbit, its preceding
    orbit should be completely filled with
    electrons according to 2n2 law.
    6. The last orbit cannot have more than 8
    electrons and its preceding orbit cannot
    have more than 18 electrons.
    The rule 2n2 is used
    up to 4 orbits.

    View full-size slide

  18. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 18
    Basic Electronics
    Ion & Ionisation:
    1. An atom remains no longer neutral if it
    gains or loses one or more electrons.
    Hence a charged atom is called an ion.
    2. An atom having a deficit of electrons is
    termed as positive ion or cation and an
    atom having a surplus of electrons is
    termed as negative ion or anion.
    3. The conversion of atoms into ions is
    known as ionization.

    View full-size slide

  19. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 19
    Basic Electronics
    How many electrons are there in atom of
    an element?
    The relative atomic mass of mercury is
    200.59.
    It means 200.59 gram of mercury shall
    have 6.023×1023 atoms.
    The each atom of mercury has 80
    electrons.
    Therefore,1 gram of Hg shall have
    240211376400000000000000 electrons.

    View full-size slide

  20. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 20
    Basic Electronics
    Inter-Atomic Bonds:
    The bond between atoms makes it possible
    to combine to form a solid.
    Inter-atomic bonds are of three main types:
    1. Metallic bond
    2. Covalent bond &
    3. Ionic bond.
    These bonds determine the electric
    conductivity of the materials.

    View full-size slide

  21. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 21
    Basic Electronics
    Metallic bond:
    This type of bond exists in metals and
    their alloys e.g. brass which is the
    combination of copper & zinc.
    Stainless steel (composed of iron,
    chromium, carbon and nickel).
    14 karat gold (composed of gold and
    copper).

    View full-size slide

  22. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 22
    Basic Electronics
    It is a connection
    between atoms
    formed by sharing,
    rather than
    transferring
    electrons.
    Covalent bond:
    Si & Ge has 4 electrons in their outer
    most orbit. They share electrons.

    View full-size slide

  23. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 23
    Basic Electronics
    Ionic bond:
    The bond taking place
    between sodium &
    chlorine.
    Sodium (11 electrons) has 1 electron in its
    outer most orbit and Chlorine (17
    electrons) has 7. For some atoms it is
    easier to lose electrons than to pick up
    new ones.

    View full-size slide

  24. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 24
    Basic Electronics
    Covalent Bond Ionic Bond

    View full-size slide

  25. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 25
    Basic Electronics
    Semiconductors
    (Diodes)

    View full-size slide

  26. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 26
    Basic Electronics
    Conductors are those who have 1, 2 or 3
    electrons in their outermost orbit. They are
    good conductors of heat & electricity.
    Insulators are those who have 6, 7 or 8.
    They are bad conductors of both heat &
    electricity.
    Semiconductors are those who have 4
    electrons & that is why they are neither
    conductors nor insulators.

    View full-size slide

  27. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 27
    Basic Electronics
    Intrinsic semiconductors are pure
    semiconductor without any impurity e.g.
    silicon & germanium.
    Extrinsic semiconductors are not pure.
    They are added with impurity. The process
    of adding impurity is called doping.
    Generally 1 to 2 atoms of impurity is
    added for 1million intrinsic atoms.

    View full-size slide

  28. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 28
    Basic Electronics
    P-type semiconductor is made when 1 or 2
    atoms of Gallium is doped with 1 million
    atoms of Silicon or Germanium.
    3+4=7 electrons means 1 hole is there.

    View full-size slide

  29. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 29
    Basic Electronics
    N-type semiconductor is made when 1 or
    2 atoms of Arsenic is doped with 1 million
    atoms of Silicon or Germanium.
    5+4=9 electrons means 1 extra electron.

    View full-size slide

  30. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 30
    Basic Electronics
    When p type and n-type semiconductors
    are diffused together; it becomes p-n
    junction.

    View full-size slide

  31. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 31
    Basic Electronics

    View full-size slide

  32. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 32
    Basic Electronics
    V-I characteristics of a p-n junction diode:
    Forward & reverse biased condition

    View full-size slide

  33. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 33
    Basic Electronics
    Half-wave rectifier

    View full-size slide

  34. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 34
    Basic Electronics
    Full-wave rectifier

    View full-size slide

  35. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 35
    Basic Electronics
    Bridge rectifier

    View full-size slide

  36. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 36
    Basic Electronics
    3-phase full wave rectifier

    View full-size slide

  37. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 37
    Basic Electronics
    Parameter Half Wave Full Wave Bridge
    No of diodes 1 2 4
    Transformer   
    DC output 0.318VS Peak
    0.636VS Peak
    0.636VS Peak
    DC output 0.45VS RMS
    0.45VS RMS
    0.45VS RMS
    Ripple factor 1.21 0.482 0.482
    Ripple Hz HzInput
    2HzInput
    2HzInput
    Efficiency 40.6% 81.2% 81.2%
    Comparison of Rectifiers

    View full-size slide

  38. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 38
    Basic Electronics
    Ripple Filters

    View full-size slide

  39. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 39
    Basic Electronics
    Ripple Filters:
    The main function of any ripple filter is to
    minimise the ripple.
    Output of various rectifier circuits is
    pulsating.
    It has a d.c. component and some a.c.
    components which are called ripples.
    This type of output is not useful for driving
    sophisticated electronic circuits/devices.

    View full-size slide

  40. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 40
    Basic Electronics
    The ratio between the rms value of ac
    component of output voltage and the dc
    components of output voltage is known as
    ripple factor.
    For the half-wave rectifier it is 1.21 & for
    the full wave 0.482.
    It can be brought to near zero by using
    ripple filters.

    View full-size slide

  41. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 41
    Basic Electronics
    There are 4 types of ripple filter.
    1. Inductor filter
    2. Capacitor filter
    3. Inductor-capacitor or LC filter
    4. П filter or CLC filter.

    View full-size slide

  42. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 42
    Basic Electronics
    Inductor filter:
    1. It is also called choke filter.
    2. It consists of an inductor L.

    View full-size slide

  43. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 43
    Basic Electronics
    3. It offers high resistance to ac but no
    resistance to dc components.
    4. More effective for heavy load currents.
    5. Results in lower dc output. Why?
    6. Ripple factor γ , f =50 Hz & L in Henry
    RL
    RL
    γ = ------------------ = ---------------------
    3√2.2Πf.L 1330L

    View full-size slide

  44. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 44
    Basic Electronics
    Capacitor filter:
    1. It is cheap filter for light loads.
    2. Capacitor allows ac to pass.

    View full-size slide

  45. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 45
    Basic Electronics
    3. Discharging time constant should be 100
    times than charging time.
    4. Capacitor maintains large voltage across
    the load resistance.
    5. Suitable for smaller ripple frequency.
    6. Ripple factor γ , f =50 Hz & C in μF.
    1 2890
    γ = ------------------ = ---------------------
    4√3.f.C.RL
    C.RL

    View full-size slide

  46. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 46
    Basic Electronics
    LC filter:
    1. In inductor filter, ripple factor is directly
    proportional to load resistance.
    2. In capacitor filter, ripple factor it is
    inversely proportional.

    View full-size slide

  47. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 47
    Basic Electronics
    3. When combined, the ripple factor will
    become independent load resistor.
    4. This is called LC filter/inductor input
    filter/choke input filter etc.
    5. Ripple factor γ , f =50 Hz & C in μF & L
    in Henry.
    √2 1.195
    γ = ------------------ = ------------------
    12.(2Πf)2 LC LC

    View full-size slide

  48. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 48
    Basic Electronics
    П filter:
    1. It is called CLC filter.
    2. It is used where low output current and
    high dc output voltage is required.

    View full-size slide

  49. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 49
    Basic Electronics
    3. DC output voltage will be high only
    when C1
    is large (the first capacitor).
    4. The ripple factor will be depending upon
    C1
    ×C2
    not on C1
    + C2
    .
    5. Ripple factor γ , f =50 Hz & C in μF & L
    in Henry.
    1 5700
    γ = --------------------------------- = --------------
    4√2.(2Πf)3.C1
    .C2
    .L.RL
    LC

    View full-size slide

  50. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 50
    Basic Electronics
    Voltage Regulators

    View full-size slide

  51. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 51
    Basic Electronics
    We all know that electronic devices needs
    constant dc voltage for their operation.
    The dc voltages can be supplied from dry
    cells or batteries.
    But these are expensive and needs
    frequent replacement or charging.
    Therefore, regulated dc power supply is
    made by converting the domestic ac supply
    i.e. 230V50 Hz.

    View full-size slide

  52. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 52
    Basic Electronics
    The essential element which constitutes a
    regulated power supply are;
    1.Rectifier 2. Filter 3.Voltage regulator.

    View full-size slide

  53. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 53
    Basic Electronics
    The main reasons of voltage fluctuations in
    an circuit is;
    1. Increase or decrease in input voltage
    2. Increase or decrease in load resistor.
    Therefore, the main task for any voltage
    regulator is to maintain constant voltage
    across the load resistor under any of the
    above 4 conditions.

    View full-size slide

  54. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 54
    Basic Electronics
    Voltage regulation in % is given by
    VMAX
    – VMIN
    = --------------------------------------- × 100
    VMAX
    Where,
    VMAX
    is the maximum dc output voltage
    VMIN
    is the minimum dc output voltage.

    View full-size slide

  55. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 55
    Basic Electronics
    Voltage regulation may also be given in %
    VNL
    – VFL
    = --------------------------------------- × 100
    VFL
    Where, VFL
    is the full load voltage & VNL
    is
    the no load or open circuit voltage of the
    supply.
    Smaller the value of voltage regulation
    better is the power supply!

    View full-size slide

  56. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 56
    Basic Electronics
    Basic types of voltage regulators:
    1. Zener diode shunt regulator
    2. Transistor shunt regulator
    3. Transistor series regulator
    4. Controlled transistor series regulator
    5. Monolithic regulator.

    View full-size slide

  57. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 57
    Basic Electronics
    Zener diode shunt regulator:
    1. Since Zener is connected in parallel, it is
    known as shunt regulator

    View full-size slide

  58. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 58
    Basic Electronics
    2. A resistance RS
    is connected in series
    with the zener to limit the current in the
    circuit.
    3. This is also known as series current
    limiting resistor.
    4. The output VL
    is taken across the RL
    .
    5. The input voltage must be greater than
    the VZ
    .

    View full-size slide

  59. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 59
    Basic Electronics
    6. The input current i.e. the current through
    the limiting resistor is given by VS
    – VZ
    divided by RS
    .
    7. VS
    is the input voltage & VZ
    is the zener
    voltage.
    8. The ideal zener diode acts as constant
    voltage source of voltage (VZ
    ).
    9. The practical zener diode has a definite
    value of resistance called rZ
    .

    View full-size slide

  60. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 60
    Basic Electronics
    10.This causes a voltage drop inside the
    zener equal to IZ
    .rZ
    .
    11.Therefore, the voltage across the
    terminals of zener is equal to load
    voltage i.e. VL
    = VZ
    + IZ
    .rZ
    .
    12.The current through the load resistor is
    given by IL
    = VL
    /RL
    .
    13.The input current IS
    = IZ
    + IL
    .
    14.This also is IZ
    = IS
    - IL
    .

    View full-size slide

  61. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 61
    Basic Electronics
    Disadvantages:
    1. The maximum load current is limited to
    IZ(MAX)
    – IZ(MIN)
    which is of few mA.
    2. A large amount of power is wasted in
    the zener diode and in series resistor.
    3. The regulation factor and the output
    resistance are not very low.

    View full-size slide

  62. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 62
    Basic Electronics
    Transistor shunt regulator:
    1. In this type of voltage regulator, a
    transistor is connected in parallel with
    the load that is why the circuit is
    named.

    View full-size slide

  63. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 63
    Basic Electronics
    2. The load voltage VL
    is equal to the sum
    of zener voltage VZ
    & VBE
    .
    3. In other words, VBE
    = VL
    – VZ
    .
    4. Since, voltage for a given zener diode is
    fixed, therefore any increase or decrease
    in load voltage will have a
    corresponding effect on the VBE
    .
    5. When VS
    increases, load voltage also
    increases.

    View full-size slide

  64. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 64
    Basic Electronics
    6. This will cause VBE
    to increase.
    7. Transistor will conduct more. IC
    will
    increase forcing VS
    & IS
    to increase.
    8. IS
    increases VRS
    . VL
    decreases.
    VS
    = VRS
    + VL
    or VL
    = VS
    – VRS
    .
    VS
    ↑→ VL
    ↑→ VBE
    ↑→ IC
    → VRS
    ↑→ VL↓

    View full-size slide

  65. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 65
    Basic Electronics
    Transistor series regulator:
    1. In this type of voltage regulator, a
    transistor is connected in series with the
    load that is why the circuit is named.
    2. This is also called emitter follower.
    3. The transistor behaves like variable
    resistance whose value is determined by
    the base current.
    4. VL
    = VZ
    – VBE
    = VZ
    – VL
    .

    View full-size slide

  66. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 66
    Basic Electronics
    5. When value of load resistance increases,
    load current decreases, load voltage
    tends to increase.
    6. Increase in load voltage will decrease
    the base-emitter voltage because zener
    is fixed.
    7. Forward bias to the transistor reduces.
    8. Less conduction, increases collector to
    emitter voltage.

    View full-size slide

  67. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 67
    Basic Electronics
    9. This decreases input current to
    compensate for the increase in the value
    of load resistor.
    10.Thus load voltage may remain at a
    constant value.
    11.The output of a transistor series
    regulator is approximately equal to the
    zener voltage VZ
    .
    12.This can be used for larger load.

    View full-size slide

  68. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 68
    Basic Electronics
    VL
    ↑→VBE
    ↓→VCE
    ↑→VZ

    Circuit Diagram
    Transistor Series Regulator
    15 V

    View full-size slide

  69. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 69
    Basic Electronics
    9. This decreases input current to
    compensate for the increase in the value
    of load resistor.
    10.Thus load voltage may remain at a
    constant value.
    11.The output of a transistor series
    regulator is approximately equal to the
    zener voltage VZ
    .
    12.This can be used for larger load.

    View full-size slide

  70. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 70
    Basic Electronics
    Voltage Multipliers

    View full-size slide

  71. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 71
    Basic Electronics
    Voltage multiplier is a circuit, which
    produces a greater dc output voltage than
    ac input voltage to the rectifiers.
    Multipliers are required in many circuits
    applications where it is necessary to have
    high voltage with low current.
    The best example is in the CRT for
    accelerating purposes.

    View full-size slide

  72. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 72
    Basic Electronics
    Voltage multipliers are generally;
    1. Half wave voltage doublers
    2. Full wave voltage doublers
    3. Voltage triplers
    4. Voltage quadrupler etc.

    View full-size slide

  73. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 73
    Basic Electronics
    Half wave voltage doublers:
    -Vm
    – Vm
    + VC2
    = 0
    VC2
    = 2Vm = 2  peak input voltage

    View full-size slide

  74. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 74
    Basic Electronics
    Full wave voltage doublers:
    During + ve half cycle D1
    conducts not D2
    .
    During - ve half cycle D2
    conducts not D1
    .

    View full-size slide

  75. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 75
    Basic Electronics
    Voltage tripler & quadruplers:
    The half wave voltage doubler circuit can
    be extended to obtain any multiple.

    View full-size slide

  76. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 76
    Basic Electronics
    Testing of diodes:

    View full-size slide

  77. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 77
    Basic Electronics
    Bi-Polar
    Junction Transistor

    View full-size slide

  78. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 78
    Basic Electronics
    T
    R
    A
    N
    S
    F
    E
    R
    R
    E
    S
    I
    S
    T
    O
    R

    View full-size slide

  79. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 79
    Basic Electronics
    It consists of two back to back p-n
    junctions manufactured in a single crystal.
    These two junctions give rise to 3 regions
    called emitter, base & collector.

    View full-size slide

  80. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 80
    Basic Electronics
    When a layer of n-type material
    sandwiched between two layers of p-type
    material, it is called p-n-p transistor.
    When p-type is sandwiched between
    layers of n-type, it is called n-p-n
    transistor.

    View full-size slide

  81. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 81
    Basic Electronics
    The emitter, base & collector are provided
    with terminals which are labeled as E, B &
    C.
    The 2 junctions are emitter-base junction
    and collector-base junction.

    View full-size slide

  82. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 82
    Basic Electronics
    The arrow head is always at the emitter.
    The arrow head indicates the conventional
    direction of current flow.
    In p-n-p, it heads from emitter to base
    means emitter is more positive than base.
    Whereas in n-p-n, it is from base to emitter
    means base is more positive than emitter.
    Transistors are made by growing, alloying
    or diffusing.

    View full-size slide

  83. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 83
    Basic Electronics
    Emitter:
    It forms the left hand section or region.
    More heavily doped.
    Its function is to supply either electrons or
    holes to the base.
    Physically it is smaller than collector but
    larger than base.

    View full-size slide

  84. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 84
    Basic Electronics
    Base:
    It forms the middle section of the transistor
    It is very thin say 10-6m as compared to
    either the emitter or collector.
    It is very lightly doped.

    View full-size slide

  85. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 85
    Basic Electronics
    Collector:
    It forms the right-hand side region.
    Main function is to collect either electrons
    or holes from the emitter and passing
    through the base.
    Physically it is largest because it has to
    dissipate much greater power.

    View full-size slide

  86. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 86
    Basic Electronics
    The best way to understand emitter, base
    & collector is to compare as;
    Emitter as water tank in your house, base
    as a water tap & collector, the water you
    collect from the water tap.
    When you want more
    water; what do you
    do? open the tap. Like
    wise, base current!

    View full-size slide

  87. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 87
    Basic Electronics
    It is essential for the working of
    transistor to apply correct polarity across
    its junction. This is called biasing.

    View full-size slide

  88. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 88
    Basic Electronics
    Emitter-base junction must be forward
    biased & collector-base junction must be
    reverse biased.
    This can be achieved by 3 ways or
    configurations.

    View full-size slide

  89. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 89
    Basic Electronics
    For a p-n-p transistor, collector & base are
    negative w.r.t. emitter.
    For n-p-n transistor it is positive w.r.t.
    emitter.

    View full-size slide

  90. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 90
    Basic Electronics
    Transistor currents:
    The three primary currents which flow in
    the properly biased transistor are;
    1. Emitter current IE
    .
    2. Base current IB
    &
    3. Collector current IC
    .
    It is seen that IE
    = IB
    + IC
    .

    View full-size slide

  91. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 91
    Basic Electronics
    By normal convention, currents flowing
    into a transistor are taken as positive.
    Current flowing out are taken as negative.
    Hence, IE
    is +ve and IB
    & IC
    are –ve.
    Applying Kirchhoff’s law, IE
    + (-IB
    ) + (-IC
    ) =0
    IE
    - IB
    – IC
    = 0 or IE
    = IB
    + IC
    This statement is true regardless of
    transistor type & configuration.

    View full-size slide

  92. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 92
    Basic Electronics
    Summing up:
    The four basic guidepost about transistor
    circuits are;
    1. Conventional current flows along arrow
    whereas electrons flow against it.
    2. Emitter-base junction is forward biased.
    3. Collector-base junction is reverse biased
    4. IE
    = IB
    + IC
    .

    View full-size slide

  93. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 93
    Basic Electronics
    Transistor circuit configuration:
    Configuration means circuit connection.
    Basic there are 3 types of circuit
    connections. They are;
    1. Common base
    2. Common emitter and
    3. Common collector.

    View full-size slide

  94. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 94
    Basic Electronics
    Common base configuration:
    In this configuration, the input signal is
    applied between base & emitter whereas
    output is taken out from base & collector.
    The ratio of collector current to the emitter
    current is known as alpha  of a transistor
     = IC
    /IE
    or IC
    =  IE
    .
    The value of  of a transistor ranges from
    0.95 to 0.99 but not equal to 1.

    View full-size slide

  95. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 95
    Basic Electronics
    Common emitter configuration:
    In this configuration, the input signal is
    applied between base & emitter whereas
    output is taken out from emitter & collector.
    The ratio of collector current to the base
    current is known as Beta  of a transistor
     = IC
    /IB
    or IC
    =  IB
    .
    The value of  of a transistor ranges up to
    500.

    View full-size slide

  96. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 96
    Basic Electronics
    Common collector configuration:
    In this configuration, the input signal is
    applied between base & collector whereas
    output is taken out from emitter & collector.
    The ratio of emitter current to the base
    current is known as Gamma  of a
    transistor
     = IE
    /IB
    or IE
    =  IB
    .

    View full-size slide

  97. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 97
    Basic Electronics
    IC
    IC
     = -------- &  = -------
    IE
    IB
    IC
    IC
    IC
    /IE

     = ----- = ---------- = --------------- = --------
    IB
    I
    E
    – IC
    IE
    /IE
    – IC
    /IE
    1 - 

    Therefore,  = ---------- &  = 1 + .
    1 + 

    View full-size slide

  98. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 98
    Basic Electronics
    The three transistor dc current always
    bear the following ratio’
    IE
    : IB
    : IC
    :: 1 : (1 - ) : 
     
     = ----------,  = ---------- &  = 1 + .
    1 +  1 - 

    View full-size slide

  99. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 99
    Basic Electronics
    Transistor has 2 main functions;
    1. As a switch &
    2. As an amplifier.
    When transistor is cut off, it means no
    current flows through it. When it is
    saturated; maximum current is flowing.
    Under both the above conditions, it can be
    made to work as a switch which has either
    ON or OFF position.

    View full-size slide

  100. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 100
    Basic Electronics
    The following sub-script is worth
    remembering.
    VCC
    : Supply voltage collector
    VEE
    : Supply voltage emitter
    VBB
    : Supply voltage base
    VCE
    : Voltage between emitter & collector.
    VCB
    : Voltage between collector & base.
    VEB
    : Voltage between emitter & base.

    View full-size slide

  101. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 101
    Basic Electronics
    Cut-off point is that point at which
    transistor doesn’t conduct any current
    means IB
    =0, IC
    =0; hence VCE
    =VCC
    .
    Considering the circuit,
    VCE
    =VCC
    -IC
    RL
    At this point, transistor is
    used as a switch;
    normally closed.

    View full-size slide

  102. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 102
    Basic Electronics
    Saturation point is that point at which
    collector carries maximum current means,
    IC
    =βIB
    ; hence VCE
    =VCC
    -IC
    RL
    .
    Considering the circuit,
    VCE
    =VCC
    -IC
    RL
    = 0
    At this point, transistor is
    used as a switch;
    normally open.

    View full-size slide

  103. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 103
    Basic Electronics
    Importance of VCE
    :
    The voltage VCE
    is very important in
    checking whether the transistor is;
    1. Defective
    2. Working in cut-off &
    3. In saturation or well into saturation.

    View full-size slide

  104. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 104
    Basic Electronics
    For amplifier operation, VCE
    =½VCC
    that is
    transistor is operated at approximately ½
    ON.
    In this way, variation in IB
    in either
    direction will control IC
    in both directions.
    In other words, when IB
    increases or
    decreases; IC
    also increases or decreases.

    View full-size slide

  105. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 105
    Basic Electronics
    Testing of transistors:

    View full-size slide

  106. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 106
    Basic Electronics
    Transistor Amplifiers

    View full-size slide

  107. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 107
    Basic Electronics
    Transistor amplifiers are classified
    according to their mode of operation.
    1. Input
    2. Output
    3. Frequency response
    4. Biasing condition &
    5. Transistor configuration.

    View full-size slide

  108. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 108
    Basic Electronics
    The description may read like this; small
    signal, class-A, CE configuration, voltage
    amplifier used in audio circuit means that;
    1. The input voltage is small
    2. Biasing condition is common emitter
    3. Output is voltage amplification.
    4. Frequency range is 20 to 20kHz.
    5. Class-A means 360° amplification.

    View full-size slide

  109. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 109
    Basic Electronics
    Common Base Amplifiers

    View full-size slide

  110. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 110
    Basic Electronics
    Characteristics of a CB amplifier:
     Very low input resistance (30-150Ω)
     Very high output resistance (500kΩ)
     Current gain <1
     Large voltage gain of about 1500
     Power gain up to 30dB.
     No phase reversal between input &
    output.

    View full-size slide

  111. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 111
    Basic Electronics
    Common Emitter Amplifiers

    View full-size slide

  112. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 112
    Basic Electronics
    Characteristics of a CE amplifier:
     Moderately low input resistance (1-2kΩ)
     Output resistance 50kΩ or large.
     Current gain  is between 300-500.
     Very high voltage gain
     Produces phase reversal i.e. input and
    output signals are 180° are out of phase

    View full-size slide

  113. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 113
    Basic Electronics
    Common Collector Amplifiers

    View full-size slide

  114. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 114
    Basic Electronics
    Characteristics of a CE amplifier:
     High input impedance (20-500kΩ)
     Low output impedance (500-1kΩ)
     High current gain i.e. 1+
     Voltage gain is less than 1.
     Power gain of 10-20dB.
     No phase reversal.

    View full-size slide

  115. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 115
    Basic Electronics
    Emitter follower:
    1. The common collector junction transistor
    amplifier is commonly called an emitter
    follower.
    2. It is so-called because the output of the
    circuit appears at the emitter of the
    transistor and it is approximately equal
    to the input voltage. That is, the output
    'follows' the input.

    View full-size slide

  116. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 116
    Basic Electronics
    3. The main parameter for a transistor is
    called "Beta" or Hfe (also called 'DC
    current gain'). This is the ratio of the
    collector current to the base current.
    4. For example, if 100μA flows into the
    base and causes a collector current of
    10mA, then the beta (Hfe) is 10/0.1 =
    100 which is a good value.
    5. Generally, the beta is between 20 and
    200.

    View full-size slide

  117. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 117
    Basic Electronics
    6. The base voltage is essentially constant
    at 0.7 to 0.8 volts with respect to the
    emitter when the transistor is
    conducting (turned on).
    7. If the base voltage is not at least 0.5
    volt more positive than the emitter, the
    transistor will conduct negligible
    current.

    View full-size slide

  118. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 118
    Basic Electronics
    8. In an emitter follower the base will be
    about 0.75 volts more positive than the
    emitter.
    9. The output of an emitter follower just
    follows the input, so the voltage gain is
    essentially one (unity).
    10. A big advantage of the emitter
    follower is it's high input impedance. It
    doesn't take much power to drive it.

    View full-size slide

  119. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 119
    Basic Electronics
    Emitter follower circuits

    View full-size slide

  120. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 120
    Basic Electronics
    Emitter follower as a voltage divider circuit
    when RL
    = 500k
    Parameter Simple circuit Emitter follower
    VL
    3.896V 3.4V
    IL
    0.0072mA 0.0068mA
    PL
    0.030359mW 0.023119mW

    View full-size slide

  121. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 121
    Basic Electronics
    Comparison of Amplifiers configurations
    Characteristics
    Common
    Base
    Common
    Emitter
    Common
    Collector
    Current gain Near unity () High () Highest (1+)
    Voltage gain High Very high Near unity
    Power gain Moderate Highest Lowest
    Input
    impedance
    Lowest Moderate Highest
    Output
    impedance
    Highest Moderate Lowest
    Phase reversal
    Input/output
    No Yes No

    View full-size slide

  122. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 122
    Basic Electronics
    Amplifier may also be classified on
    amount of transistor biasing and
    amplitude of the signal.
    The main classifications are;
    Class-A
    Class-B
    Class-C
    Class-AB

    View full-size slide

  123. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 123
    Basic Electronics
    Class-A Amplifiers: The transistor is so
    biased that it remains forward biased
    throughout the input cycle. This results
    output current to flow for the full cycle of
    the input signal.

    View full-size slide

  124. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 124
    Basic Electronics
    Class-B Amplifiers: The transistor is so
    biased that it remains forward biased
    only for half input cycle. This results
    output current to flow for half cycle of the
    input signal.

    View full-size slide

  125. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 125
    Basic Electronics
    Class-C Amplifiers: The transistor is so
    biased that it remains forward biased for
    less than half input cycle. This results
    output current to flow for less than half
    cycle i.e. 120-150° the input signal.

    View full-size slide

  126. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 126
    Basic Electronics
    Class-AB Amplifiers: The transistor is so
    biased that it remains forward biased for
    more than half input cycle. This results
    output current to flow for more than half
    cycle i.e. 180° but less than 360° of the
    input signal.
    Its characteristics lies somewhere
    between those of class-A & class-B.

    View full-size slide

  127. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 127
    Basic Electronics
    Class-B Push-Pull Amplifiers:
     It employs two identical transistors
    operating as a single stage of
    amplification.

    View full-size slide

  128. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 128
    Basic Electronics
    2. They are CE in configuration.
    3. Transistor A takes positive half cycle
    whereas B handles negative half cycle.
    4. The two outputs are combined.
    5. Whenever there is no signal, it doesn’t
    draw any power from the VCC
    .
    6. Used extensively in audio work like
    receivers, tape-recorders etc.

    View full-size slide

  129. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 129
    Basic Electronics
    Advantages:
     Efficiency is up to 75%.
     Distortion free output.
     No saturation of the transformer cores.
     No power is drawn in the absence of the
    input signal.

    View full-size slide

  130. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 130
    Basic Electronics
    Disadvantages:
     It requires bulky and expensive output
    transformers.
     It requires two out of phase input
    signals which necessitates an input
    centre tapped transformer.
     Driver circuit becomes very complicated.

    View full-size slide

  131. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 131
    Basic Electronics
    Complementary symmetry class-B push-
    pull amplifier:
    1. Complementary amplifier is a pair of
    closely matched but oppositely doped
    power transistors.

    View full-size slide

  132. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 132
    Basic Electronics
    2. Complementary amplifier is a pair of
    closely matched but oppositely doped
    power transistors.
    3. One transistor is PNP but another NPN
    4. They operate as emitter follower.
    5. Input is capacitive coupled whereas
    output is direct.
    6. Transistors do not conduct when input
    signal is not present.

    View full-size slide

  133. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 133
    Basic Electronics
    7. Positive going input signal forces
    transistor A to conduct and B to cut-off.
    8. Push-pull goes on as one is conducting
    & another goes to cut-off.
    9. Unity voltage gain, no phase reversal &
    high input impedance.
    10.Frequency not a limitations since there
    is no transformer.
    11.Less weight.

    View full-size slide

  134. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 134
    Basic Electronics
    Amplifier couplings

    View full-size slide

  135. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 135
    Basic Electronics
    When the output of one amplifier is
    connected to the input of another
    amplifier via something; then it is called
    coupling. The four basic method of
    couplings are;
    1. Resistance-capacitance coupling.
    2. Impedance or Inductive coupling
    3. Transformer coupling &
    4. Direct coupling.

    View full-size slide

  136. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 136
    Basic Electronics
    R-C coupling: Amplifiers using this type of
    coupling are known as RC coupled
    amplifiers. This consists of two single
    stage transistor amplifiers using CE
    configuration.

    View full-size slide

  137. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 137
    Basic Electronics
    The resistors R2
    & R3
    and capacitor C2
    forms the coupling. Capacitor C1
    couples
    the input signal whereas C3
    couples out
    the output signal.
    The input vi
    is amplified by transistor
    Q1
    .The dc component is blocked by C2
    and signal is further amplified by Q2
    .
    The output signal is twice of the input
    signal with no phase reversal.

    View full-size slide

  138. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 138
    Basic Electronics
    Advantages:
    1. Expensive or bulky components are not
    required. Hence, small, light & simple.
    2. Overall amplification is higher.
    3. Minimum distortions since coils,
    transformers etc. are not used.
    4. Very flat frequency verses gain curve. It
    gives uniform voltage amplification over
    wide range.

    View full-size slide

  139. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 139
    Basic Electronics
    Disadvantages:
    1. Not suitable for very low or very high
    frequency due to capacitive reactance.
    2. Large voltage drops across collector
    load resistors.

    View full-size slide

  140. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 140
    Basic Electronics
    L-C coupling: Amplifiers using this type of
    coupling are known as impedance
    coupled amplifiers. This consists of two
    single stage transistor amplifiers using
    CE configuration.

    View full-size slide

  141. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 141
    Basic Electronics
    Advantages:
    1. Hardly any drop across L; hence low
    collector supply voltage can be used.
    Disadvantages:
    1. Larger, heavier and costlier.
    2. Needs protection from magnetic field.
    3. Frequency response is not as good as
    of RC coupling.

    View full-size slide

  142. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 142
    Basic Electronics
    At low frequencies, the gain is low due to
    large capacitance offered by the
    capacitor.
    Gain remains low even at high
    frequencies, due to large reactance.
    LC coupling is
    therefore suitable
    only for audio
    frequencies.

    View full-size slide

  143. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 143
    Basic Electronics
    Transformer coupling: Amplifiers using
    this type of coupling are known as
    transformer coupled amplifiers. This
    consists of two single stage transistor
    amplifiers using CE configuration.

    View full-size slide

  144. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 144
    Basic Electronics
    T1
    is the coupling transformer whereas T2
    is the output transformer.C1
    is the input
    coupling capacitor whereas C2
    , C3
    & C4
    are the bypass capacitors.
    Resistors R1
    and R2
    as well as R4
    and R5
    form voltage divider circuits whereas R3
    and R6
    are emitter stabilising resistors.
    When input signal is coupled through C1
    to the base of Q1
    , it appears in an
    amplified form in the primary of T1
    .

    View full-size slide

  145. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 145
    Basic Electronics
    The secondary of T1
    applies the signal to
    the base of Q2
    which appears in an
    amplified form in the primary of T2
    .
    The secondary of T2
    finally appears
    across the matched load R7
    .
    Advantages:
    1.More efficient because of low dc
    resistance in the primary of collector.
    2.It provides higher voltage gain.

    View full-size slide

  146. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 146
    Basic Electronics
    3. Poor frequency response because
    transformer is frequency sensitive.
    4. Provides impedance matching.
    Disadvantages:
    1. Costly, bulky & expensive.
    2. Faces problem at radio frequencies.
    3. Poor frequency response
    4. Tends to introduce hum.

    View full-size slide

  147. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 147
    Basic Electronics
    The peak gain
    occurs due to
    resonance or tuning
    effect of inductance
    and distributed
    capacitance.
    Frequency response:
    At low frequencies, primary reactance is
    small, the gain is less.

    View full-size slide

  148. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 148
    Basic Electronics
    Direct coupling: These amplifiers operate
    without the use of frequency sensitive
    components like capacitors, inductors and
    transformers.

    View full-size slide

  149. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 149
    Basic Electronics
    They are specially suited for amplifying
    1. AC signals with frequencies as low as
    a fraction of a hertz.
    2. Change in dc voltages.
    3. Any signal current at the base of Q1
    is
    amplified β1
    times and appears at the
    collector of Q1
    and becomes base signal
    for Q2
    .
    Current gain = β1
     β2

    View full-size slide

  150. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 150
    Basic Electronics
    Advantages:
    1. Circuit arrangement is very simple &
    cheap since it uses minimum
    components.
    2. Capable of amplifying signals of low
    frequency.
    Disadvantages:
    1. It can’t amplify high frequency signals.

    View full-size slide

  151. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 151
    Basic Electronics
    2. Poor temperature stability.
    Applications:
    1. Regulator circuits of electronic power
    supply units.
    2. Pulse amplifiers
    3. Differential amplifiers
    4. Electronic instruments
    5. Computer circuitry.

    View full-size slide

  152. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 152
    Basic Electronics
    Darlington pair:
    It is the name given
    to a pair of similar
    transistors, so
    connected that
    emitter of one is
    directly joined to the
    base of the other as
    shown below.

    View full-size slide

  153. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 153
    Basic Electronics
    Darlington pairs are commercially
    mounted in a single package that has
    only 3 leads.
    The main characteristics of Darlington
    pairs are;
    1. Current gain
    2. Input impedance and
    3. Voltage gain.

    View full-size slide

  154. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 154
    Basic Electronics
    Advantages:
    1. It can be readily formed from two
    adjacent transistors in an IC.
    2. It can transform a low impedance load
    into a high impedance load.
    3. It uses very few components.
    4. It provides vary high β values.

    View full-size slide

  155. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 155
    Basic Electronics
    Load Line

    View full-size slide

  156. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 156
    Basic Electronics
    Load lines and DC bias circuits:
    The straight line joining cut-off and
    saturation points of a BJT is called load
    line.
    Load line can be
    drawn when VCC
    &
    RL
    is known.

    View full-size slide

  157. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 157
    Basic Electronics
    Given:
    VCE
    =VCC
    =30V
    IC(Sat)
    = 6mA
    IB
    =30/1.5M=20μA &
    IC
    = βIB
    =10020=2mA
    VCE
    =VCC
    -IC
    RL
    =30-(25)=20V
    Hence, Q point is 20V;2mA

    View full-size slide

  158. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 158
    Basic Electronics
    Q-point:
    The middle point of extreme points (cut-
    off & saturation) on the load line, is
    known as Quiescent point or Q-point.
    The Q-point can be fixed from the data of
    a transistor given in transistor data
    books. This reduces the time consuming
    work of plotting the collector
    characteristics and the load line.

    View full-size slide

  159. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 159
    Basic Electronics
    To do so, the following are very
    important to remember.
    1.The chosen VCC
    must be less than
    VCE(Max)
    given in the data book. As far
    as possible, value of VCC
    must be
    restricted to ¾ of VCE(Max)
    .
    2.Fix the Q-point IC
    at ½ of IC(Max)
    given in
    the data book.
    3.At the Q-point assume ½ of VCC
    will be
    across VCE
    .

    View full-size slide

  160. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 160
    Basic Electronics
    4. From points (2) & (3), find the value of RC
    .
    5. From the HFE
    value given in data book, fix
    the approximate value of the base current
    at the Q-point as given below;
    6. Chosen value of IC
    at the Q-point
    IB
    at Q-point = ----------------------------------------------
    Typical value of HFE
    from data book.
    7. From the value of IB
    at the Q-point and
    allowing a 0.7 volts drop across the base-
    emitter, calculate the value of RB
    .

    View full-size slide

  161. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 161
    Basic Electronics
    Electronic Oscillators

    View full-size slide

  162. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 162
    Basic Electronics
    Electronic Oscillators:
    1. It is a circuit which converts dc energy
    into ac energy at very high frequency.
    2. A source of generating sine, square,
    saw tooth or pulse shape.
    3. Generates ac output without any
    external applied input.
    4. It is an unstable amplifier.

    View full-size slide

  163. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 163
    Basic Electronics
    Comparison
    Amplifier & Oscillator

    View full-size slide

  164. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 164
    Basic Electronics
    Classification:
    Electronic oscillator may broadly be
    divided into following two groups.
    1. Sinusoidal (harmonic) oscillator
    2. Non-sinusoidal (relaxation) oscillator.

    View full-size slide

  165. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 165
    Basic Electronics
    Sinusoidal oscillator produce an output
    having sine waveform. This may further
    be divided in to;
    1. Tuned circuits or LC feedback
    oscillators such as Hartley, Colpitts,
    Clapp etc.
    2. RC phase shift e.g. Wien bridge
    3. Negative resistance oscillators such
    as tunnel diode.

    View full-size slide

  166. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 166
    Basic Electronics
    4. Crystal oscillators
    5. Heterodyne or beat frequency
    oscillators.
    The active devices (BJT’s, FET’s &
    UJT’s) in the abovementioned circuits
    may be biased as class-A, AB, B or C.
    Class-A biasing is used in high quality
    AF oscillators whereas RF oscillators
    prefer class-C biasing.

    View full-size slide

  167. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 167
    Basic Electronics
    Damped oscillations:
    Oscillations whose amplitude keeps
    decreasing with time.
    This is due to the I2R losses taking place
    continuously.

    View full-size slide

  168. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 168
    Basic Electronics
    Un-damped oscillations:
    Oscillations whose amplitude remains
    constant i.e. doesn’t change with time.
    I2R losses taking place; is compensated
    continuously.

    View full-size slide

  169. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 169
    Basic Electronics
    Oscillatory circuit:
    1. It is also called LC or tank circuit.
    2. This circuit consists of two reactive
    elements; an inductor & a capacitor.
    3. Both are capable of storing energy.
    4. Capacitor stores energy in its electric
    field whenever there is potential
    difference across its plates.

    View full-size slide

  170. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 170
    Basic Electronics
    5. Similarly, an inductor stores energy in
    its magnetic field whenever current
    flow through it.
    6. Both L & C are suppose to be loss
    free.
    7. Let that the capacitor has been fully
    charged from a dc source.
    8. Since, S is open, it can not discharge
    through L

    View full-size slide

  171. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 171
    Basic Electronics
    Working of tank circuit

    View full-size slide

  172. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 172
    Basic Electronics
    When switch ‘S’ is closed;
    1. Electrons move from plate A to plate B
    through coil L.
    2. Coil L opposes the flow of current but
    some current does pass.
    3. Magnetic field is set up in L which
    stores the energy.
    4. When plate A loses all its electrons,
    current stops.

    View full-size slide

  173. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 173
    Basic Electronics
    5. Magnetic field set in the coil,
    collapses, emf is induced and
    according to Lenzs’ law; current flow
    but in the opposite direction i.e. from
    plate B to plate A.
    6. Now capacitor starts getting charged
    but in opposite direction till the time
    potential becomes equal.
    7. Once, capacitor is charged fully, it
    again discharges through L.

    View full-size slide

  174. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 174
    Basic Electronics
    8. This sequence of charging and
    discharging continues. The to and fro
    motion of electrons between the two
    plates of capacitor constitutes an
    oscillatory current.
    9. It may be noted that during this
    process, the electrical energy of the
    capacitor is converted into magnetic
    energy of the coil and vice-versa.

    View full-size slide

  175. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 175
    Basic Electronics
    10.These oscillations are damped
    because energy is dissipated and
    their amplitude becomes zero.
    11.There are two reasons for this loss of
    energy.
     heat produced in the resistance of
    the coil and connecting wires.
     in the form of EM waves that are
    radiated out due to oscillation.

    View full-size slide

  176. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 176
    Basic Electronics
    The frequency or the time period of the
    oscillatory current depends upon;
    1. Larger the value of capacitor, greater
    the charging and discharging time.
    2. Larger the self induction, greater the
    time required for each reversal.
    1 159
    f = ----------- = --------- kHz
    2Π√LC √LC
    L in μH &
    C in μF

    View full-size slide

  177. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 177
    Basic Electronics
    Essential of a feedback LC oscillator:
    1. Tank circuit or FDN
    2. Amplifier 3. A positive feedback.

    View full-size slide

  178. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 178
    Basic Electronics
    Tuned base oscillator:
    1. R1
    , R2
    & R3
    determines dc biasing.
    2. L1
    & L are mutually coupled forming
    primary & secondary of RF
    transformer for feedback between CB.
    3. CE connected transistor provides 180°
    phase shift between input & output.
    4. Output transformer provides another
    180° phase shift & total becomes 360.

    View full-size slide

  179. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 179
    Basic Electronics
    5. The parallel tuned LC circuit connected
    between the base & emitter is FDN.
    Circuit operation:
    1. When ‘S’ is closed, IC
    increases.
    2. L1
    & L expands.
    3. EB voltage & current increases.
    4. Further increase in IC
    .
    5. Increase in feedback.

    View full-size slide

  180. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 180
    Basic Electronics
    Tuned base oscillator

    View full-size slide

  181. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 181
    Basic Electronics
    6. IC
    goes in to saturation.
    7. Meanwhile C gets charged.
    8. When no increase in IC
    , L1
    contracts.
    9. Less feedback through L.
    10.C starts discharging.
    11.Decrease in the voltage of C,
    decreases EB voltage, IC
    , L1
    and
    finally IC to cut-off.

    View full-size slide

  182. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 182
    Basic Electronics
    12. After losing its original charge,
    capacitor again becomes fully
    charged though with opposite
    polarity.
    13. Since, transistor is in cut-off state,
    capacitor discharges through L.
    14. EB, IC
    , L1
    & L increases that drives
    transistor into saturation.
    15. This cycle keeps on repeating.

    View full-size slide

  183. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 183
    Basic Electronics
    Tuned collector oscillator:
    1. L1
    C1
    forms primary winding &
    combination an oscillatory tank circuit.
    2. Positive feedback between CE & EB is
    provided by transformer secondary
    winding L2
    which is mutually coupled
    to L1
    .
    3. AC signal is connected through L2
    to
    emitter via low reactance C2
    & C3
    .

    View full-size slide

  184. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 184
    Basic Electronics
    4. CE configuration gives 180° phase
    shift and another 180° is given by
    transformer.
    5. R1
    & R2
    is used for dc biasing.
    Working:
    1. When switch is on, a transient current
    is developed in the L1
    C1
    circuit.
    2. This initiates natural oscillation.

    View full-size slide

  185. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 185
    Basic Electronics
    3. Small emf induced in L2
    by mutual
    inductance causes increase in IB
    .
    4. IB is amplified β times & appears in
    collector circuit.
    5. Part of this amplified energy is used
    to meet loses.
    6. The frequency of oscillatory current is
    almost equal to resonant frequency.

    View full-size slide

  186. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 186
    Basic Electronics
    Circuit of tuned collector oscillator
    Let,
    Inductance = 100μH
    fo
    = 1500kHz
    What should be the C?
    C = 133pF!

    View full-size slide

  187. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 187
    Basic Electronics
    Hartley oscillator:
    1. Invented by Ralph Hartley in 1915.
    2. Inductively coupled, variable frequency
    oscillators where the oscillator may be
    series or shunt fed.
    3. Series fed oscillators have poor
    oscillation stability.
    4. Shunt fed are used in radio receivers.

    View full-size slide

  188. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 188
    Basic Electronics
    Practical Hartley Oscillator

    View full-size slide

  189. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 189
    Basic Electronics
    5. Tank circuit has centre tapped inductor
    and one tuning capacitor.
    6. The RF choke at the collector keeps the
    high frequency ac signal out of VCC
    .
    7. RF choke may be replaced with a
    resistor in cheaper oscillators.
    8. Hartley oscillator coil has three
    connections i.e. T, P & G. The resistance
    between T & P < T & G.

    View full-size slide

  190. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 190
    Basic Electronics
    9. The oscillator frequency range is in
    MHz.
    10. It can be varied by varying C1
    .
    11. The frequency may be measured;
    i. Frequency counter (Direct Read
    Out)
    ii. Oscilloscope

    View full-size slide

  191. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 191
    Basic Electronics
    Advantages:
    1. The frequency is simply varied by the
    net value of C in the tank circuit.
    2. The output amplitude remains
    constant when tuned over the
    frequency range.
    3. The feedback ratio of L1
    to L2
    remains
    constant.

    View full-size slide

  192. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 192
    Basic Electronics
    Disadvantages:
    1. The output is rich in harmonic
    content.
    2. Not suitable where a pure sine wave
    is required.

    View full-size slide

  193. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 193
    Basic Electronics
    Colpitts oscillator:
    1. Invented by Edwin H Colpitts.
    2. Key features of this type of oscillator is
    its simplicity and robustness.
    3. It is similar to Hartley oscillator except
    using split capacitor in tank circuit.
    4. Generally used for frequencies > 1MHz.

    View full-size slide

  194. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 194
    Basic Electronics
    Colpitts Oscillator

    View full-size slide

  195. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 195
    Basic Electronics
    Crystal oscillators:
    1. When mechanical stress is applied
    across the two opposite faces of a
    crystal, a potential difference is
    developed across them. It is called
    Piezo-electric effect.
    2. Also, when a potential difference is
    applied across its two opposite faces,
    it causes the crystal to expand or
    contract.

    View full-size slide

  196. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 196
    Basic Electronics
    3. If an ac is applied, the crystal is set
    into vibration.
    4. The frequency of vibration is equal to
    the resonant frequency of the crystal
    which is determined by its structure.
    5. When the frequency of the ac equals
    the resonant frequency, the amplitude
    of vibration is maximum.
    6. Thinner the crystal higher is vibration.

    View full-size slide

  197. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 197
    Basic Electronics
    Pierce Crystal oscillator
    Applications:
    1.Mobile
    2.Transmitters
    3.Test equipment
    4.Precise work

    View full-size slide

  198. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 198
    Basic Electronics
    Wien bridge oscillators:
    1. Suitable for generating low frequencies
    in the range of 10Hz to 1MHz.
    2. It uses two CE connected RC coupled
    amplifiers and one RC (Wien) bridge.
    3. To avoid more components, they use
    operational amplifiers.
    4. Highly stabilised amplitude, voltage &
    frequency.

    View full-size slide

  199. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 199
    Basic Electronics
    Wien bridge oscillator

    View full-size slide

  200. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 200
    Basic Electronics
    Non-Sinusoidal (Relaxation) Oscillators:
    1. Those oscillators which generate
    waveforms other than sine waveform
    are called non-sinusoidal oscillator.
    2. They are also called relaxation
    oscillator.
    3. That include square, rectangular, saw-
    tooth & pulse shaped.

    View full-size slide

  201. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 201
    Basic Electronics
    Square wave Saw tooth wave
    Triangular wave Rectangular wave

    View full-size slide

  202. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 202
    Basic Electronics
    Pulse width 1μs
    MSR = -------------------- = --------------= 1:4
    Time between pulse 4μs
    PRT (Pulse Repetition Time): Time
    between beginning of one pulse and that
    of the other.
    PRF (Pulse repetition Frequency): It is
    number of pulses per second.

    View full-size slide

  203. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 203
    Basic Electronics
    Pulse definition:
    Time delay td: It is the time interval
    between the beginning of the input pulse
    and the time the output voltage reaches
    10% of its maximum value.
    Rise time tr: It is the time taken by the
    output voltage to rise from 10% to 90% of
    its maximum value.
    Turn-on Time TON
    : = td + tr.

    View full-size slide

  204. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 204
    Basic Electronics
    Pulse definition:

    View full-size slide

  205. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 205
    Basic Electronics
    Pulse width: It is the time duration of the
    output pulse measured between two
    50% levels of the output pulse.
    Storage Time ts: Time interval between
    end of the input pulse and the time
    when output voltage falls to 90%.
    Fall Time tf: Time interval during which
    the output voltage falls from 90% to 10%.
    Turn-off Time TOFF
    = ts + tf.

    View full-size slide

  206. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 206
    Basic Electronics
    Multi-vibrators:
    1. These devices are useful as pulse
    generating, storing & counting circuits.
    2. They are two stage amplifiers with
    positive feedback from the output of
    one amplifier to the input of second
    amplifier.
    3. The feedback is supplied in such a
    way that one transistor is driven to

    View full-size slide

  207. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 207
    Basic Electronics
    saturation and other to cut-off.
    4. New set of conditions in which the
    saturated transistor is driven to cut-
    off and the cut-off to saturation.
    5. Three basic types of multi-vibrators;
    i. Astable
    ii. Bistable &
    iii. Monostable

    View full-size slide

  208. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 208
    Basic Electronics
    Astable multi-vibrator (AMV):
     It is also called free running relaxation
    oscillator.
     It has no stable state but keeps
    oscillating between two states of its
    own without any external excitation.
     When one is on, the other is off & they
    continuously switch back & forth at a
    rate depending on RC time constant.

    View full-size slide

  209. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 209
    Basic Electronics
    4. Hence, it oscillates and produces
    pulses of certain MSR.

    View full-size slide

  210. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 210
    Basic Electronics
    When the power is switched on, one of
    the transistor will start conducting before
    the other.
    Let Q1
    starts conducting first. The
    feedback is such that Q1
    will be very
    rapidly driven to saturation and Q2
    to
    cut-off.
    Soon, Q1
    will come to cut-off and make
    Q2
    to saturation and this goes on.

    View full-size slide

  211. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 211
    Basic Electronics
    Mono-stable multi-vibrator (MMV):
     It is also called single shot or one shot.
     It has one stable state.
     It can be switched to other state by an
    external trigger pulse.
     But it returns to the previous state
    after a time delay determined by the
    value of circuit components.

    View full-size slide

  212. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 212
    Basic Electronics
    5. It has one energy storing element.

    View full-size slide

  213. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 213
    Basic Electronics
    The initial stable state is represented by
    Q2
    conducting & Q1
    at cut-off.
    When trigger pulse is applied, this multi-
    vibrator switches Q2
    to cut-off and Q1
    to
    conducting.
    Soon, it returns to initial stage by the
    feedback . It remains in this state till
    another trigger pulse arrives.
    The pulse duration T = 0.69C1
    R1
    .

    View full-size slide

  214. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 214
    Basic Electronics
    Bi-stable Multi-vibrator (BMV):
     It is called flip-flop multi-vibrator.
     It has two absolute stable state.
     It can remain in either of these two
    states unless an external trigger pulse
    switches it from one state to the other.
     It doesn’t oscillates.
     It has no energy storage element.

    View full-size slide

  215. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 215
    Basic Electronics
    4. Hence, it oscillates and produces
    pulses of certain MSR.

    View full-size slide

  216. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 216
    Basic Electronics
    Whenever, a positive pulse is applied to
    R, Q2
    starts conducting. Collector of Q2
    falls to zero & cuts-off Q1
    .
    When positive pulse is applied to S, it
    brings multi-vibrator to its original state.
    It is widely used in computer memory
    circuits, counting circuits & frequency
    dividing circuit.

    View full-size slide

  217. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 217
    Basic Electronics
    Schmitt Trigger
    1. It is named after its inventor.
    2. It closely resembles a multi-vibrator.
    3. It has two bi-stable states.
    4. It is also called emitter coupled binary
    oscillator because positive feedback
    occurs by coupling through emitter
    resistor RE
    .

    View full-size slide

  218. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 218
    Basic Electronics
    4. Hence, it oscillates and produces
    pulses of certain MSR.

    View full-size slide

  219. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 219
    Basic Electronics
    Applications:
    1. It is frequently used for wave shaping
    purposes even worn out pulses.
    2. It can convert inputs with any wave
    shape into output pulses having
    rectangular or square wave shapes.
    3. This circuit is often called squarer.
    4. It can be used as level detector.

    View full-size slide

  220. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 220
    Basic Electronics
    Uni-polar Junction
    Transistor (UJT)
    Field Effect Transistors

    View full-size slide

  221. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 221
    Basic Electronics
    Field effect transistor:
    1. The FET’s were developed in 1960.
    2. Current conduction is done by the flow
    of one type of carrier i.e. holes or
    electrons.
    3. Current is controlled by the effect of
    electric field.
    4. This has an extremely high input
    resistance ≈100 M).

    View full-size slide

  222. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 222
    Basic Electronics
    5. They are voltage controlled divices.
    6. It shows high degree of insulation
    between input and output.
    7. The FET is less noisy than a tube or
    BJT.
    8. More suitable for input stages of low
    signal amplifier.
    9. It is mostly used in high fidelity FM
    receivers.

    View full-size slide

  223. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 223
    Basic Electronics
    There are two types of FET;
    i. JEFT (Junction Field Effect
    Transistor).&
    ii. MOSFET (Metal Oxide
    Semiconductor FET).

    View full-size slide

  224. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 224
    Basic Electronics
    JEFT are fabricated by two ways;
    (I) p-channel
    (II) n-channel

    View full-size slide

  225. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 225
    Basic Electronics
    n-channel:
    n-channel JFET is constructed using a
    bar of N-type material into which a pair
    of P-type are diffused.
    Three wires are connected to device.

    View full-size slide

  226. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 226
    Basic Electronics
    One at each end of the channel and the
    third at the substrate.
    In a sense, this device is like a pn
    junction diode except that we have
    connected two wires to the n-side.
    Electrons can move along the channel
    When we apply a voltage between the
    two end wires, a current will flow along
    the channel.

    View full-size slide

  227. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 227
    Basic Electronics
    The flow of electrons from source to
    drain will depend upon the upon the
    size and shape of the channel and the
    properties of the N-type material.
    When a small –ve voltage through the
    third wire is given to the substrate, the
    depletion zones get bigger.
    Current flow becomes difficult and even
    stops. This is called pinching off the
    current.

    View full-size slide

  228. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 228
    Basic Electronics
    The third current is called gate because
    it can be used to control the flow of
    electrons along the channel.
    If we want to increase the current, a
    small +ve voltage to the gate needs to be
    applied which will make depletion zone
    smaller.

    View full-size slide

  229. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 229
    Basic Electronics
    If we apply too large +ve gate voltage
    we will make it possible for channel
    electrons to cross the walls and move
    into the substrate.
    What’s is worse, modern FET’s have
    such tiny gates that even a small
    channel-gate will blow up the transistor.
    A basic rule in practical electronics.
    Transistors blow up faster than fuses!

    View full-size slide

  230. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 230
    Basic Electronics
    Comparison between FET & BJT:
    i. FET is uni-polar device i.e. current in
    the device is carried either by the
    electrons or by the holes whereas BJT
    is bipolar device i.e. current is carried
    by both electrons and the holes.
    ii. FET is voltage controlled device
    whereas BJT is current controlled.

    View full-size slide

  231. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 231
    Basic Electronics
    iii.FET’s input resistance is of several
    mega ohms whereas input resistance
    of BJT is of few kilo ohms.
    iv. FET has a positive temperature
    coefficient at high current levels &
    this characteristic prevents the FET
    from thermal breakdown. BJT has a
    negative temperature coefficient at
    high current level & this characteristic
    leads the BJT to thermal breakdown.

    View full-size slide

  232. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 232
    Basic Electronics
    v. FET doesn’t suffer from minority
    carrier storage effects and therefore
    has higher switching speeds and cut
    off frequencies but BJT’s do suffer
    from minority carriers storage effects
    and therefore BJT has both lower
    switching speed and cut off
    frequencies than that of FET’s.
    vi.Fabrication of FET’s on IC is simpler
    than BJT’s.

    View full-size slide

  233. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 233
    Basic Electronics
    Biasing of JFET:
    1. Gates are always reverse biased.
    Therefore the gate current IG
    is
    practically zero.
    2. In a n-channel JFET, source channel
    S is connected to the negative of the
    DC power supply. And, the positive of
    the DC power supply is connected to
    the drain terminal of the JFET.

    View full-size slide

  234. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 234
    Basic Electronics
    iii.In the p-channel JFET, source is
    connected to the positive end of the
    power supply and the drain is
    connected to the negative end of the
    power supply unit for the drain to get
    the holes from the p-channel where
    the holes are the majority carriers.

    View full-size slide

  235. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 235
    Basic Electronics
    Applications:
    1. As input amplifiers in oscilloscopes,
    electronic measuring instruments etc.
    as it doesn’t load much to circuit due
    to its high impedance.
    2. For mixer operations in FM receivers.

    View full-size slide

  236. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 236
    Basic Electronics
    3. In logic circuits where it is kept off
    when there is zero input and is
    turned on with a very little input
    power.
    4. As voltage variable resistor (VVR) in
    operational amplifier and tone control
    circuits.
    5. LSI and computer memories because
    of very small size.

    View full-size slide

  237. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 237
    Basic Electronics
    Testing of JFET and MOSFET:
    1. Measure the resistance by a
    multimeter between source and drain.
    Its value should be about 10 k.
    2. Multimeter should indicate low
    resistance between gate and source
    with one polarity and indicate very
    high resistance between source and
    drain when the polarity is changed.

    View full-size slide

  238. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 238
    Basic Electronics
    3. When the gate junction is open, it
    gives high resistance with both the
    polarities. When junction is shorted, it
    gives low resistance.
    4. While checking MOSFET, the value of
    resistance between gate and drain
    should be infinitely high in either
    polarity. If it gives low resistance, the
    device is faulty.

    View full-size slide

  239. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 239
    Basic Electronics
    Step Gate Source Drain
    Measured Resistance
    Good FET Bad FET
    1 open -ve +ve very low high/very high
    2 open +ve -ve very low high/very high
    3 -ve open +ve very high low/very low
    4 +ve open -ve very low high
    5 -ve +ve open low low
    6 +ve -ve open low high

    View full-size slide

  240. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 240
    Basic Electronics
    MOSFET:
    Is abbreviated for metal oxide
    semiconductor field effect transistor.
    It has a source, gate and drain. The gate
    of the MOSFET is insulated from the
    channel.
    Because of this, it is sometimes known
    as IGFET (Insulated Gate Field Effect
    Transistor).

    View full-size slide

  241. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 241
    Basic Electronics
    MOSFET’s are of two types namely
    depletion type MOSFET and Enhance-
    type MOSFET.

    View full-size slide

  242. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 242
    Basic Electronics
    n-Channel MOSFET/IGFET
    Depletion type Enhancement type
    (Less current) (More current)

    View full-size slide

  243. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 243
    Basic Electronics
    p-Channel MOSFET/IGFET
    Depletion type Enhancement type
    (Less current) (More current)

    View full-size slide

  244. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 244
    Basic Electronics
    Integrated MOSFET

    View full-size slide

  245. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 245
    Basic Electronics
    Integrated Circuits
    IC-741 & IC-555

    View full-size slide

  246. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 246
    Basic Electronics
    Integrated Circuits:
    Is an integrated (put together) form of
    several components of a circuit on a
    single chip or wafer of a semiconductor
    material, generally silicon.
    IC’s may have
    hundreds of active
    and passive
    components.

    View full-size slide

  247. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 247
    Basic Electronics
    Active components such as diodes and
    transistors take much less space on the
    chip than resistors and capacitors.
    Transistors are used as resistors instead
    of fabricating resistors themselves.
    Components like choke, coils and
    transformers cannot be fabricated in IC’s
    because of its physical bulkiness.

    View full-size slide

  248. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 248
    Basic Electronics
    Therefore, wherever inductors are
    necessary for a circuit leads are brought
    out of the IC’s such that inductors can be
    connected externally to the IC.
    Most IC’s are designed to be used for
    more than one application by making
    small changes in external circuitry. For
    example, an IC may be used as an
    amplifier or as an oscillator and so on.

    View full-size slide

  249. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 249
    Basic Electronics
    Advantages of IC’s:
    1. Miniaturization of the electronic
    gadgets.
    2. Drastic decrease in the overall weight.
    3. Low power requirement.
    4. Increased reliability due to less
    number of solder connections.

    View full-size slide

  250. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 250
    Basic Electronics
    5. Greater flexibility in use of the same IC
    for circuit configurations.
    6. Better functioning under wide range of
    temperatures.
    7. Low cost per IC due to large scale
    production of IC’s.
    8. Easy to replace.

    View full-size slide

  251. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 251
    Basic Electronics
    Limitations:
    1. Large value capacitors and resistors
    cannot be fabricated.
    2. Chokes, inductors and transformers
    cannot be fabricated.
    3. If any one stage inside the IC becomes
    defective, the complete IC has to be
    discarded.
    4. Handling is very delicate.

    View full-size slide

  252. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 252
    Basic Electronics
    Operational Amplifiers:
    1. Often referred as Op-Amps is a high
    gain, direct coupled differential
    amplifier, designed to amplify both DC
    and AC signals.
    2. In early days these amplifiers were
    used in analogue computers to perform
    mathematical operations such as
    addition, multiplication etc.
    3. That is why it is called “operational.”

    View full-size slide

  253. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 253
    Basic Electronics
    4. It has two inputs and one output.
    5. It have a special type of amplifier
    configuration known as differential
    amplifier as its first stage.

    View full-size slide

  254. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 254
    Basic Electronics
    Differential amplifiers stage:
    1. A differential amplifier stage consists
    of two transistors with an input to
    each transistor.
    2. The output is taken between the
    collectors of the transistors as shown.
    3. The most important point to note is,
    both the transistors have identical
    characteristics, load resistors, input
    resistors and a single emitter resistor.

    View full-size slide

  255. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 255
    Basic Electronics
    4. Dual power supply (+ve, -ve and GND)
    is required for differential amplifiers
    (single supply can also be used with a
    few extra components).

    View full-size slide

  256. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 256
    Basic Electronics
    If a dual supply is used & if the amplifier
    is properly balanced (symmetrical
    values) the output voltage across the
    collectors will be equal to the difference
    of the two input voltages. Hence, this
    amplifier is called differential amplifier
    It can be operated in two modes;
    1. Common-mode operation
    2. Differential-mode operation.

    View full-size slide

  257. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 257
    Basic Electronics
    Common mode operation:
    Since both sides of the differential
    amplifier circuits are identical, if an
    additional signal of same level and
    phase is applied to both the inputs, the
    same output signal results from both
    collectors. Mathematically;
    VOUT (COM)
    = A (V1
    – V2
    )

    View full-size slide

  258. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 258
    Basic Electronics
    Where A is the voltage gain of each
    transistor & V1
    & V2
    are the base input
    voltages measured to ground.
    If both the signals
    are same in phase
    & in magnitudes;
    VOUT
    = A (V1
    – V2
    )
    = A (V1
    – V1
    )
    = A (0) = 0

    View full-size slide

  259. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 259
    Basic Electronics
    Where A is the voltage gain of each
    transistor & V1
    & V2
    are the base input
    voltages measured to ground.
    In practice, since the two halves of the
    circuit cannot be perfectly identical,
    instead of zero output there will be a
    very small output.
    When inputs are 0.5 V, output in common
    mode may be 0.025V not zero? Why?

    View full-size slide

  260. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 260
    Basic Electronics
    Differential mode operation:
    When two inputs signals are out of phase
    by 180°, the amplifier amplifies the
    difference of the input signals.
    Since, the input signals are of equal in
    amplitude, but out of phase by 180°, the
    output signal is equal to twice the gain
    times the input signal.

    View full-size slide

  261. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 261
    Basic Electronics
    This can be mathematically written as;
    VOUT (DIFF)
    = A [V1
    -(-V2
    )]
    If V1
    = V2
    then
    VOUT (DIFF)
    = A (2V1
    )

    View full-size slide

  262. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 262
    Basic Electronics
    Common mode rejection ratio:
    The advantage of differential amplifiers
    is, it doesn’t amplify input signals that
    are in phase. This is known as common-
    mode signal rejection.
    CMRR = ADM
    /ACM
    .
    ADM = Amplifier gain in differential mode
    ACM = Amplifier gain in common mode.

    View full-size slide

  263. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 263
    Basic Electronics
    Inverting amplifier:
    The input signal is applied to the
    inverting ‘+’ (INV) terminal. The non
    (NON) inverting terminal is grounded.
    The output is amplified signal of opposite
    polarity.

    View full-size slide

  264. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 264
    Basic Electronics
    Non-inverting amplifier:
    The input signal is applied to the non-
    inverting ‘-’ (NON) terminal. The inverting
    (INV) terminal is grounded. The output is
    amplified signal of in phase polarity.

    View full-size slide

  265. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 265
    Basic Electronics
    Summing amplifier:
    Operational amplifier is used as an
    inverting amplifier to do the summing
    operation.

    View full-size slide

  266. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 266
    Basic Electronics
    In the given figure, three input signals
    are applied to the INV terminal through
    resistors R1
    , R2
    & R3
    .
    The amount of negative feedback given to
    the OP amplifier is dependent on the
    value of RF divided by each resistor in
    the feedback path.

    View full-size slide

  267. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 267
    Basic Electronics
    RF
    RF
    RF
    V (OUT)
    = (   V1
    ) + (   V2
    ) + (   V3
    )
    R1
    R1
    R1
    If, R1
    , R2
    , R3
    = RF
    , then RF
    /R becomes 1 in
    each signal path. Then output is given
    V (OUT)
    = V1
    + V2
    + V3
    = (1  1V) + (1  2V) + (1  3V)
    = 1 + 2 + 3
    = 6 Volts.

    View full-size slide

  268. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 268
    Basic Electronics
    Schematic diagram of IC-741

    View full-size slide

  269. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 269
    Basic Electronics
    Timer IC-555:
    Applications such as square wave, ramp,
    pulse generators and one shot multi-
    vibrators etc. require a circuit essentially
    capable of producing timing intervals.
    Due to the circuit components count and
    the delicacy in using transistors,
    integrated circuits are preferred to
    transistors.

    View full-size slide

  270. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 270
    Basic Electronics
    One such most suitable and popular IC
    for producing time intervals is the 555.
    This IC is popularly known as 555 timer.
    Similar to operational amplifier, 555 IC is
    reliable, easy to use in a variety of
    applications, and at low cost. The IC 555
    can operate from a wide range of supply
    voltages of + 5 to + 18 volts.

    View full-size slide

  271. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 271
    Basic Electronics
    IC-555 contains
    i. Two comparators
    ii. One transistor
    iii.Three equal value resistors
    iv.One flip-flop and
    v. An output stage.

    View full-size slide

  272. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 272
    Basic Electronics
    This makes 555 compatible with
    standard digital circuits.

    View full-size slide

  273. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 273
    Basic Electronics
    Modes of operation:
    The timer has two modes of operation;
    1.As an astable (free running) &
    2.As a mono-stable (one shot).

    View full-size slide

  274. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 274
    Basic Electronics
    Principle of operation:
    1. The threshold input is connected to an
    external RC timing circuit.
    2. If the capacitor charge exceeds the
    ⅔VCC
    , reference on the threshold
    comparator, the comparator is
    triggered.
    3. This sets the flip-flop.
    4. Turns on the transistor.
    5. Capacitor discharges.

    View full-size slide

  275. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 275
    Basic Electronics
    Application of astable multi-vibrator:
    1. In electronic Pianos: generation of
    different frequencies with different RC
    values.
    2. Signal injectors: used as testing
    instrument by service technicians.
    3. Flashing lights: advertisements,
    displays etc.

    View full-size slide

  276. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 276
    Basic Electronics
    IC-555 timer as VCO:
    A voltage controlled
    oscillator (VCO)
    changes its output
    frequencies in relation
    to the input voltage at
    the control input of the
    threshold comparator
    at pin-5.

    View full-size slide

  277. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 277
    Basic Electronics
    Schematic diagram of security alarm

    View full-size slide

  278. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 278
    Basic Electronics
    Special Purposes
    Semiconductor Diodes

    View full-size slide

  279. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 279
    Basic Electronics
    Varactor diode:
    In a p-n junction diode, a very thin
    depletion region (an insulator) exists on
    either side of p-n type semiconductor
    materials. This forms a capacitor.

    View full-size slide

  280. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 280
    Basic Electronics
    Since, the width of the depletion region
    (dielectric) between the two plates of the
    capacitor can be varied by varying the
    external voltage applied to the junction,
    the effective capacitance of the junction
    also varied accordingly.
    Therefore, a p-n junction can be used as a
    voltage variable capacitor (VVC).
    By changing C, frequency is changed.

    View full-size slide

  281. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 281
    Basic Electronics
    Applications:
    1. Since the junction capacitance of a
    varactor diode is in the picofarad
    range, it is suitable for use in high
    frequency circuits.
    2. Automatic frequency control device.
    3. FM modulator
    4. Adjustable band pass filter and
    5. Parametric amplifiers

    View full-size slide

  282. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 282
    Basic Electronics
    Schottky diodes:
    1. It is also called Schottky barrier diode
    and hot carrier diode.
    2. Unlike the semiconductors p-n junction
    diodes, the Schottky diodes consist of a
    metal semiconductor junction.
    3. The semiconductor is normally n-type
    silicon, while a host of different metal,
    such as molybdenum, platinum,
    chrome or tungsten are used.

    View full-size slide

  283. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 283
    Basic Electronics
    4. In both materials (semiconductor and
    metal), the electron is the majority
    carrier.
    5. Therefore, the Schottky diodes are
    majority carrier device, in contrast to
    an ordinary p-n junction diode.

    View full-size slide

  284. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 284
    Basic Electronics
    This diode possesses 2 unique features.
    It is a unipolar device because it has
    electrons as majority carriers on both
    sides of the junction. An ordinary p-n
    junction diode is a bipolar device because
    it has both electrons and holes as
    majority carriers.
    No holes available in metal. Hence, no
    depletion layer, no stored charge etc. very
    less switching time.

    View full-size slide

  285. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 285
    Basic Electronics
    Applications:
    1. Widely used in clipping and clamping
    circuits, computer gating, mixing and
    detecting networks used in
    communication systems.
    2. Schottky diode can easily rectify
    signals of frequencies exceeding 300
    MHz.

    View full-size slide

  286. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 286
    Basic Electronics
    3. It can produce an almost perfect half-
    wave rectified output. The present
    maximum current rating of the device is
    about 100 A.
    4. It is commonly used in switching power
    supplies that operate at frequencies of
    20 GHz.
    5. Low noise which is extremely important
    in communication receivers and radar
    units etc.

    View full-size slide

  287. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 287
    Basic Electronics
    Tunnel diodes:
    1. This diode differ from any other diode
    discussed so far in that it has a
    magnetic resistance region.
    2. An increases in terminal voltage results
    in a reduction in diode current.
    3. By increasing the doping level of the
    material from which a p-n junction is
    formed, the depletion region may be
    reduced.

    View full-size slide

  288. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 288
    Basic Electronics
    4. It is this thin depletion region that
    many carriers can tunnel through or
    cross the junction without any external
    applied voltage.

    View full-size slide

  289. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 289
    Basic Electronics
    Applications:
    1. As an ultrahigh speed switch due to
    tunnelling mechanism which
    essentially takes place at the speed of
    light. It has a switching time of the
    order of nanosecond or even
    picosecond.
    2. As logic memory storage device due to
    triple-valued feature of its curve for
    current.

    View full-size slide

  290. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 290
    Basic Electronics
    3. As microwave oscillator at a frequency
    of about 10 GHz due to its extremely
    small capacitance and inductance and
    negative resistance.
    4. In relaxation oscillator circuits due to
    its negative resistance
    5. As an amplifier due to its negative
    resistance.

    View full-size slide

  291. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 291
    Basic Electronics
    Step Recovery Diode:
    1. It is another type of VVC (Variable
    Voltage Capacitor) diode having a
    graded doping profile where doping
    density decreases near the junction as
    shown in the figure. This results in the
    production of strong electric fields on
    both sides of the junction.
    2. Sometimes called a snap diode.

    View full-size slide

  292. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 292
    Basic Electronics
    Applications:
    1. Used in pulse and digital circuits for
    generating very fast pulses, frequency
    multipliers with rise time of less than 1
    nanosecond.

    View full-size slide

  293. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 293
    Basic Electronics
    LED:
    1. LED stands for light emitting diode.
    2. In all semiconductor p-n junctions some
    of this energy will be given off as heat
    and some in the form of light (or
    photons).
    3. In silicon and germanium diodes, the
    greater percentage is given up in the
    form of heat and the emitted light is
    insignificant.

    View full-size slide

  294. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 294
    Basic Electronics
    4. In other materials such as gallium
    arsenide phosphide (GaAsP) or gallium
    phosphide (GaP), the number of
    photons of light energy emitted is
    sufficient to create a very visible light
    source.

    View full-size slide

  295. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 295
    Basic Electronics
    OSRAM produces LED,s that radiate red,
    green, yellow, blue, orange or infrared
    (invisible light).
    Research are in full swing to replace
    discharge lamps with LED’s because;
    i. LED’s have longer life up to
    100,000 hours.
    ii. It consumes very less power i.e.
    150mW.

    View full-size slide

  296. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 296
    Basic Electronics
    Applications:
    1. Infrared LED’s are used in burglar
    alarm systems.
    2. For solid-state video displays which
    are rapidly replacing cathode ray
    tubes.
    3. In image sensing circuits used for
    picture phone.
    4. For numeric displays in hand-held or
    pocket calculators.

    View full-size slide

  297. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 297
    Basic Electronics
    5. In the field of optical communication
    where high-radiance GaAs diodes are
    matched into the silica-fibre optical
    cable.
    6. In arrays of different types for
    displaying alphanumeric (letters &
    numbers) or supplying input power to
    lasers or for entering information into
    optical computer memories.

    View full-size slide

  298. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 298
    Basic Electronics
    PIN Photo Diode:
    1. It is a three-region reverse-biased
    junction diode as shown below.
    2. A layer of intrinsic silicon is
    sandwiched between two heavily
    doped p and n type silicon materials.
    3. This has the effect of reducing the
    transit time of photo-induced electron-
    hole pair.

    View full-size slide

  299. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 299
    Basic Electronics
    4. These diodes have faster response
    than even the p-n photodiode.
    Moreover, the relative thick I-layer
    (about 2.5 m) ensures the absorption
    of most of the incident light.

    View full-size slide

  300. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 300
    Basic Electronics
    Advantages:
    1. The reverse current increases linearly
    with the level of illumination.
    2. Capable of processing very weak
    signals. Hence, such devices are
    widely used for detecting laser pulses
    and in ultra fast switching and logic
    circuits.
    3. They have broad spectral response
    and generate very low noise.

    View full-size slide

  301. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 301
    Basic Electronics
    P-N Junction Photo Diode:
    1. It is a two-terminal junction device,
    which is operated by first reverse-
    biasing the junction and then
    illuminating it.

    View full-size slide

  302. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 302
    Basic Electronics
    2. A reverse-biased p-n junction has a
    small amount of reverse saturation
    current IS (or IO) due to thermally
    generated electron-hole pair.
    3. In silicon, IS
    is in the range of
    nanoampere. The number of these
    minority carriers depends on the
    intensity of light incident on the
    junction.

    View full-size slide

  303. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 303
    Basic Electronics
    4. By changing the illumination level,
    reversed current can be changed. In
    this way, reverse resistance of the
    diode can be changed by a factor
    nearly 20.
    5. A photodiode can turn its current ON
    and OFF in nanosecond. Hence, it is
    one of the fastest photo detectors. It is
    used where it is required to switch light
    ON and OFF at maximum rate

    View full-size slide

  304. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 304
    Basic Electronics
    Applications:
    1. Detection (both visible and un visible)
    2. Demodulation
    3. Logic circuits that require stability and
    high speed.
    4. Switching
    5. Optical communication equipment
    6. Character recognising
    7. Encoders

    View full-size slide

  305. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 305
    Basic Electronics
    Laser Diode:
    1. LASER: Light amplification by
    stimulated emission of radiation.
    2. Similar to LED, LASER diodes are used
    to convert the electrical signals into
    light signals.
    3. Processes very weak signals. Hence,
    widely used for detecting laser pulses
    and in ultra fast switching and logic
    circuits.

    View full-size slide

  306. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 306
    Basic Electronics
    3. They have broad spectral response
    and generate very low noise.

    View full-size slide

  307. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 307
    Basic Electronics
    Properties:
    1. They are small.
    2. They possess high radiance (i.e., they
    emit lots of light in a small area).
    3. The emitting area is small, comparable
    to the dimensions of optical fibers.
    4. They have a very long life, offering high
    reliability.

    View full-size slide

  308. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 308
    Basic Electronics
    5. They can be modulated (turned off and
    on) at high speeds.

    View full-size slide

  309. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 309
    Basic Electronics
    GUNN Diode:
    1. In 1963, Gunn discovered the
    transferred electron effect known as
    GUNN effect & is used for generation of
    microwave oscillations.

    View full-size slide

  310. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 310
    Basic Electronics
    Power Diode:
    1. Known as rectifier & is used to convert
    a.c to d.c.
    2. PIV ratings 50 to 1200 volts.
    3. Current rating 30 to 40 A or even more.
    4. Is constructed using silicon.
    5. The forward resistance of power diodes
    must be as small as possible but the
    reverse resistance must be as large as
    possible.

    View full-size slide

  311. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 311
    Basic Electronics
    IMPATT Diode:
    1. IMPATT diode stands for INPact
    Avalanche and Transit Time Diode.
    2. When alternating voltage is applied,
    current will rise when voltage falls.
    3. Hence, negative resistance may be
    redefined as that property of the
    device, which causes the current
    through it to be 180 out of phase with
    the voltage across it.

    View full-size slide

  312. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 312
    Basic Electronics
    4. IMPATT diodes are most powerful CW
    solid-state microwave power
    sources.OA-75, OA-79 etc.

    View full-size slide

  313. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 313
    Basic Electronics
    Breakdown Devices
    or
    Thyristors

    View full-size slide

  314. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 314
    Basic Electronics
    Thyristors:
    1. The term Thyristor pertains generally to
    the family of semi-conductor devices
    used for control of power.
    2. This term is derived from thyratron and
    transistor, the thyratron, being a gas-
    filled tube & transistor.
    3. They are also referred as breakdown
    devices because their working depends
    on avalanche breakdown.

    View full-size slide

  315. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 315
    Basic Electronics
    4. Thyristor means family of four-layer
    solid-state devices.
    5. It can be externally controlled by either
    current or voltage.
    6. It is a fast switching semi-conductor
    device i.e. μs/ns.
    7. Modulation of power can vary from 100
    watt to 100 mega watt.

    View full-size slide

  316. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 316
    Basic Electronics
    The thyristor is suitable for the control of
    large amounts of power because
    1. It is light in weight.
    2. Reliable
    3. Fast acting
    4. Turns on with a small power and
    5. Free from mechanical troubles.

    View full-size slide

  317. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 317
    Basic Electronics
    The following most popular thyrisitors:
    1. SCR (Silicon Controlled Rectifier)
    2. GCS (Gate Controlled Switch)/GTO
    (Gate Turn Off) Switch.
    3. SCS (Silicon Controlled Switch)
    4. Triac
    5. Diac and
    6. UJT (Uni Junction Transistor)

    View full-size slide

  318. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 318
    Basic Electronics
    SCR (Silicon Controlled Rectifier):
     It is one of the prominent members of
    the thyristor family.
     It is a four-layer or PNPN device.
     Basically, it is a rectifier with a control
    element and can be employed as a
    control switch for performing various
    functions such as rectification,
    inversion and regulation of power flow.

    View full-size slide

  319. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 319
    Basic Electronics
    4. In fact, it consists of three diodes
    connected back-to-back with a gate
    connection.
    5. It is widely used as a switching device
    in power control applications.
    6. It possesses the advantages of a
    rheostat and a switch with none of
    their disadvantages.

    View full-size slide

  320. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 320
    Basic Electronics
    Construction & biasing:

    View full-size slide

  321. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 321
    Basic Electronics
    Two transistor analogy:
    To understand the basic operation of an
    SCR, SCR is split into 3 layer transistor
    structure as shown.

    View full-size slide

  322. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 322
    Basic Electronics
    As seen, transistor Q1
    is a pnp where as
    Q2
    is an npn device connected together. It
    is also noted that the;
    1. IC
    of Q1
    is the IB
    of Q2
    &
    2. IB
    of Q1
    is the IC
    of Q2
    .
    Let the supply voltage across terminals A
    & C is such that its reverse bias junction
    J2
    starts breaking down.
    Then current through the device rises.

    View full-size slide

  323. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 323
    Basic Electronics
    The following action takes place;
    1. IE1
    begins to increase.
    2. IC1
    increases (IC
    = λIE
    )
    3. Since IC1
    = IB2
    , IB2
    increases.
    4. Hence, IC2
    increases (IC
    = βIB
    ).
    5. Now, IC2
    = IB1
    , hence IB1
    increases.
    6. Consequently, both IC1
    & IE1
    increases.

    View full-size slide

  324. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 324
    Basic Electronics
    Thus a regenerative action takes place
    whereby an initial increase in current
    produces further increase in the same
    current.
    Soon maximum current is reached limited
    by external resistance.
    The two transistors are fully turned ON
    and voltage across the two transistors
    falls to a very low value.
    This regeneration takes 0.1 to 1μs.

    View full-size slide

  325. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 325
    Basic Electronics
    Method of turning-ON:
    The SCR can be switched ON;
    1. either by increasing the forward
    voltage beyond forward break-over
    voltage (VBO
    ).
    2. by applying a positive gate signal
    when the device is forward biased
    The gate control method is more efficient.

    View full-size slide

  326. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 326
    Basic Electronics
    Consideration for gate control method:
    1. Appropriate gate to cathode voltage.
    2. The gate signal must be removed after
    the device is turned ON.
    3. No gate signal should be applied when
    the device is reverse biased.
    4. When the device is in the off-state, a
    negative voltage applied between the
    gate and the cathode will improve the
    characteristics of the device.

    View full-size slide

  327. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 327
    Basic Electronics
    Methods of turning ON the device:
    1. Triggering by d.c. gate signal.
    2. Triggering by a.c. gate signal.
    3. Triggering by pulse-gate signal.

    View full-size slide

  328. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 328
    Basic Electronics
    Methods of turning OFF the device:
    1. Natural commutation
    2. Reverse biasing
    3. Gate turn OFF
    Natural commutation: When the anode
    current is reduced below the level of the
    holding current, the SCR turns OFF.
    Generally, the anode current is 1000
    times of holding current.

    View full-size slide

  329. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 329
    Basic Electronics
    Reverse bias turn OFF:
    A reverse anode to cathode voltage (the
    cathode is positive with respect to the
    anode) will tend to interrupt the anode
    current.
    Gate turn OFF:
    In some specially designed SCR’s,
    negative gate current increases the
    holding current so that it exceeds the load
    current and device turns OFF.

    View full-size slide

  330. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 330
    Basic Electronics
    Half-wave power control:
    SCR’s are commonly used for control of
    a.c. power for lamp dimmers, electric
    heaters and motors etc.

    View full-size slide

  331. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 331
    Basic Electronics
    Controlled rectification:
    It is that rectification in which the output
    of a rectifier circuit can be varied by
    controlling the point in an ac cycle at
    which the circuit is turned ON.

    View full-size slide

  332. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 332
    Basic Electronics
    Output waveforms
    for different firing angles:

    View full-size slide

  333. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 333
    Basic Electronics
    Output voltage & current values
    Value of θ Vdc
    Idc
    0° 0.318Vm
    0.318Vm
    /RL
    30° 0.297Vm
    0.297Vm
    /RL
    45° 0.270Vm
    0.270Vm
    /RL
    60° 0.239Vm
    0.239Vm
    /RL
    90° 0.159Vm
    0.159Vm
    /RL
    120° 0.080Vm
    0.080Vm
    /RL
    135° 0.046Vm
    0.046Vm
    /RL

    View full-size slide

  334. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 334
    Basic Electronics
    Applications:
    1. Power control
    2. Relay control
    3. Regulated power supply
    4. Motor control
    5. Inverters
    6. Battery chargers
    7. Heater control
    8. Phase control

    View full-size slide

  335. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 335
    Basic Electronics
    DC motor speed control

    View full-size slide

  336. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 336
    Basic Electronics
    Over Voltage Protection

    View full-size slide

  337. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 337
    Basic Electronics
    Zero Voltage Switching

    View full-size slide

  338. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 338
    Basic Electronics
    Automatic battery charger

    View full-size slide

  339. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 339
    Basic Electronics
    Emergency light

    View full-size slide

  340. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 340
    Basic Electronics
    TRIAC:
    It is a five layer bi-directional device.
    It behaves like two SCR’s connected in
    parallel upside down with respect to each
    other.

    View full-size slide

  341. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 341
    Basic Electronics
    This can be triggered into conduction by
    both positive & negative voltages at its
    anodes and with both positive and
    negative triggering pulses at its gate.
    It responds to both +ve & -ve voltages at
    the anode, the concept of cathode used
    for an SCR is dropped.
    The two electrodes are denoted by A1
    &
    A2
    & gate G.

    View full-size slide

  342. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 342
    Basic Electronics
    Operation: When A2
    is positive:
    When positive voltage is applied to A2
    ,
    path of current flow is P1
    -N1
    -P2
    -N2
    . The
    two junctions, P1
    -N1
    & P2
    -N2
    are forward
    biased whereas N1
    -P2
    junction is blocked.
    The gate can be given either positive or
    negative voltage to turn ON the TRIAC.
    1. Positive gate: Forward biases P2
    -N2
    .
    2. Negative gate: Forward biases P2
    -N3
    .

    View full-size slide

  343. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 343
    Basic Electronics
    Operation: When A1
    is positive:
    When positive voltage is applied to A1
    ,
    path of current flow is P2
    -N1
    -P1
    -N4
    . The
    two junctions, P2
    -N1
    & P1
    -N4
    are forward
    biased whereas N1
    -P1
    junction is blocked.
    The gate can be given either positive or
    negative voltage to turn ON the TRIAC.
    1. Positive gate: Forward biases P2
    -N2
    .
    2. Negative gate: Forward biases P2
    -N4
    .

    View full-size slide

  344. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 344
    Basic Electronics
    Applications:
    1. As static switch to turn ac power
    OFF-ON.
    2. Minimising radio interference.
    3. Light, motor speed control etc.
    Disadvantages:
    Takes longer time to recover OFF state. Its
    use is limited to ac supply up to 400 Hz.

    View full-size slide

  345. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 345
    Basic Electronics
    Fan regulator using TRIAC

    View full-size slide

  346. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 346
    Basic Electronics
    Three Phase a.c. switches

    View full-size slide

  347. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 347
    Basic Electronics
    DIAC:
    A TRIAC without gate terminal is DIAC.
    It is a pair of inverted four layer diodes.
    When anode A1
    is
    positive, the current
    path is P2
    -N2
    -P1
    -N1
    .
    When anode A2
    is
    positive, the current
    path is P1
    -N2
    -P2
    -N3
    .

    View full-size slide

  348. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 348
    Basic Electronics
    The operation of DIAC is similar to two
    diodes connected in series.
    Voltage applied across it in either
    direction turns ON one diode, reverse
    biasing the other.
    Hence, it can be switched from OFF to ON
    state for either polarity of the applied
    voltage.
    Used as triggering devices in TRIAC
    phase control circuits.

    View full-size slide

  349. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 349
    Basic Electronics
    Uni-Junction Transistor (UJT):
    1. It is a three terminal silicon diode.
    2. It has only one p-n junction.
    3. It differs from ordinary diode that it
    has 3 leads.
    4. Differs from FET that it has no ability to
    amplify.
    5. It has the ability to control a large ac
    power with a small signal.

    View full-size slide

  350. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 350
    Basic Electronics
    6. It exhibits a negative resistance which
    makes it useful as an oscillator.
    7. It has one emitter E
    and two bases B2
    & B1
    .
    8. The emitter leg is
    drawn at an angle
    and arrow conven-
    tional current.

    View full-size slide

  351. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 351
    Basic Electronics
    Inter-base resistance (RBB
    ) = RB1
    + RB2
    when emitter is open.
    Point A should be at point where RB1
    >RB2
    .
    Usually, RB1
    = 60% of RB2
    .

    View full-size slide

  352. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 352
    Basic Electronics
    Intrinsic stand-off ratio:
    As seen in the figure, when a battery of
    30V is applied across B1
    & B2
    , there is a
    progressive fall of voltage over RBB
    provided emitter is open.
    It is obvious from the figure that emitter
    acts as a voltage divider tap on fixed
    resistance RBB
    .
    I1
    = I2
    = VBB
    /RBB
    (Ohm’s law)

    View full-size slide

  353. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 353
    Basic Electronics
    The voltage division factor is known as
    “intrinsic stand-off ratio” & is given by a
    special symbol .
    RB1
     = ------------------
    RB1
    + RB2
     VA
    =  VBB
    .

    View full-size slide

  354. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 354
    Basic Electronics
    Applications:
    Due to the unique property that it can be
    triggered/output can be taken from any
    one of its three terminals.
    Once triggered, the emitter current IE of
    the UJT increases re-generatively till its
    reaches limiting value determined by the
    external power supply.

    View full-size slide

  355. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 355
    Basic Electronics
    UJT’s are used in;
    1. Phase control
    2. Switching
    3. Pulse generation
    4. Sine-wave generator
    5. Saw tooth generator
    6. Timing circuits &
    7. Voltage & current regulated supplies.

    View full-size slide

  356. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 356
    Basic Electronics
    UJT as sawtooth generator:
    It consists of a power source, a uni-
    junction transistor and a R-C network.

    View full-size slide

  357. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 357
    Basic Electronics
    Circuit action:
    When S is initially closed, following chain
    of events take place.
    1. A small current is set up through R2
    and R1
    via B2
    and B1
    and an initial
    reverse bias is established across the
    EB1
    junction.
    2. C begins to get charged through RE
    and reaches target voltage V.

    View full-size slide

  358. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 358
    Basic Electronics
    3. When capacitor voltage equals the
    emitter firing voltage VP
    , EB1
    junction
    becomes forward-biased and emitter
    goes into negative region of its
    characteristics.
    4. Being forward biased, EB1
    junction
    offers very low resistance. Hence, C
    starts discharging through B1
    and R1
    at a rate determined mainly by EB1
    junction resistance and R1
    .

    View full-size slide

  359. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 359
    Basic Electronics
    5. As capacitor voltage approaches zero,
    the EB1
    junction again becomes
    reverse-biased and so stops
    conducting.
    6. Thus, we revert to the initial stage
    where C begins to charge and the
    whole cycle is repeated.
    The slow charge and fast discharge
    produces a saw-tooth wave.

    View full-size slide

  360. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 360
    Basic Electronics
    We have seen the applications of
    Electronics. Much more is yet to be
    discovered.
    What to say about the studies of Protonics
    & Neutronics?
    Our life and our surroundings are full of
    mysteries. Science has helped us to
    discover to some extent.

    View full-size slide

  361. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 361
    Basic Electronics
    Zener Diode

    View full-size slide

  362. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 362
    Basic Electronics
    Zener Diode

    View full-size slide

  363. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 363
    Basic Electronics
    Zener Diode

    View full-size slide

  364. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 364
    Basic Electronics
    Zener Diode

    View full-size slide

  365. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 365
    Basic Electronics
    Shunt Voltage Regulator

    View full-size slide

  366. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 366
    Basic Electronics
    Shunt Voltage Regulator

    View full-size slide

  367. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 367
    Basic Electronics
    Voltage Doubler Circuit

    View full-size slide

  368. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 368
    Basic Electronics
    Voltage Doubler Circuit

    View full-size slide

  369. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 369
    Basic Electronics
    Voltage Doubler Circuit

    View full-size slide

  370. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 370
    Basic Electronics
    Push Pull Amplifiers

    View full-size slide

  371. Basic Electronics
    May 2006 SG Jha , Training Centre, OSRAM INDIA Private Limited, Sonepat Slide: 371
    Basic Electronics
    Push Pull Amplifiers

    View full-size slide