Analog electronics circuits miscellaneous


Analog electronics circuits miscellaneous

Analog Electronic Circuits

  1. Single stage transformer coupled class A amplifier is delivering the a.c. power to the load of 1.25 watts. The d.c. power from the d.c. supply is:









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    NA

    Correct Option: B

    NA


  1. Single stage transformer coupled class A power amplifier uses a transistor with maximum dissipation capability of 2.5 watts. The maximum a.c. power in the load is:









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    In class A transformer coupled

    η = 0·5 =
    Po(ac)
    Pi(dc)

    where,
    Po(ac) → maximum ac power in the load
    Pi(dc) → maximum applied dc power to the amplifier
    given that PD (max) = 2.5
    0.5 =
    Po(ac)
    PD(max) + Po(ac)

    0.5 =
    Po(ac)
    2.5 + Po(ac)

    1.25 + 0.5 Po (ac) = Po (ac)
    0.5 Po (ac) = 1.25
    or Po (ac) =
    1·25
    = 2.5 watts.
    ·5

    Correct Option: B

    In class A transformer coupled

    η = 0·5 =
    Po(ac)
    Pi(dc)

    where,
    Po(ac) → maximum ac power in the load
    Pi(dc) → maximum applied dc power to the amplifier
    given that PD (max) = 2.5
    0.5 =
    Po(ac)
    PD(max) + Po(ac)

    0.5 =
    Po(ac)
    2.5 + Po(ac)

    1.25 + 0.5 Po (ac) = Po (ac)
    0.5 Po (ac) = 1.25
    or Po (ac) =
    1·25
    = 2.5 watts.
    ·5



  1. In a class A series fed amplifier using a transistor, under conditions the maximum ac power delivered is 1 watt.
    The maximum transistor dissipation capability should be:









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    Given Po(ac) max = 1 watt
    PD (max) =?

    Again 0.5 = η =
    Po(ac)
    Pi(dc)

    or 0.5 =
    Po(ac)
    PD(max) + Po(ac)

    or 0.5 =
    1
    PD(max) + 1

    or 0.5 PD (max) + 0.5 = 1
    or 0.5 PD (max) = 0.5
    or PD (max) = 1
    Hence alternative (A) is the correct choice.

    Correct Option: A

    Given Po(ac) max = 1 watt
    PD (max) =?

    Again 0.5 = η =
    Po(ac)
    Pi(dc)

    or 0.5 =
    Po(ac)
    PD(max) + Po(ac)

    or 0.5 =
    1
    PD(max) + 1

    or 0.5 PD (max) + 0.5 = 1
    or 0.5 PD (max) = 0.5
    or PD (max) = 1
    Hence alternative (A) is the correct choice.


  1. In class A direct coupled (series fed) power amplifier, maximum dissipation capability of the transistor is 2.5 watts, when delivering maximum a.c. power in the load is:









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    Given PD Max = 2.5 Watts
    Poac =?
    We know maximum efficiency of direct coupled class-A amplifier is 50% i.e., η = 50%

    η = 50% = 0.5 =
    Po(ac)
    Pi(dc)

    ∴ Pi (dc) = Po (ac) + PD) Pi (dc)
    = Po (ac) + 2.5
    or 0.5 =
    Po(ac)
    Po(ac) + 2·5

    or 0.5Po(ac) + 1.25 = Po (ac)
    or 0.5 Po (ac) = 1.25
    or Po (ac) =
    1·25
    = 2.5 watts.
    0·5

    where, Po (ac) = output ac power to the load
    Pi (dc) = input dc power to the transistor

    Correct Option: B

    Given PD Max = 2.5 Watts
    Poac =?
    We know maximum efficiency of direct coupled class-A amplifier is 50% i.e., η = 50%

    η = 50% = 0.5 =
    Po(ac)
    Pi(dc)

    ∴ Pi (dc) = Po (ac) + PD) Pi (dc)
    = Po (ac) + 2.5
    or 0.5 =
    Po(ac)
    Po(ac) + 2·5

    or 0.5Po(ac) + 1.25 = Po (ac)
    or 0.5 Po (ac) = 1.25
    or Po (ac) =
    1·25
    = 2.5 watts.
    0·5

    where, Po (ac) = output ac power to the load
    Pi (dc) = input dc power to the transistor



  1. For the resonant circuit shown, w0 = 105, Q = 50, R = 400Ω. The value of C is given by:











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    Q =
    ω0L
    R

    50 =
    105·L
    400

    L = 0.2
    Also ω01 =
    1
    LC

    or ω02 =
    1
    or C =
    1
    =
    1
    LCω02·L(105)2 × 0·2

    = 500 pf


    Correct Option: C

    Q =
    ω0L
    R

    50 =
    105·L
    400

    L = 0.2
    Also ω01 =
    1
    LC

    or ω02 =
    1
    or C =
    1
    =
    1
    LCω02·L(105)2 × 0·2

    = 500 pf