Analog circuits miscellaneous


Analog circuits miscellaneous

  1. An amplifier has an open loop gain of 100, an input impedance of 1kΩ, and an out put impedance of 100 Ω. If a feedback network with a feedback factor of 0.99 is connected in a voltage series feedback mode then new input and output impedances are
    (a)
    (b)
    (c)









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    Zif = Zi (1 + βA) = 1 k (1 + 100 × 0.99) = 100 kΩ

    Zof =
    Z0
    =
    100
    = 1 Ω
    1 + βA100

    Correct Option: C

    Zif = Zi (1 + βA) = 1 k (1 + 100 × 0.99) = 100 kΩ

    Zof =
    Z0
    =
    100
    = 1 Ω
    1 + βA100


  1. In the circuit shown in the given figure, the type of feedback used is










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    NA

    Correct Option: B

    NA



  1. In the single-stage transistor amplifier circuit shown in the given figure, if capacitor CE is removed, then, ac small-signal midband voltage gain of the amplifier










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    With CE, voltage gain

    Aυ = -
    -hfeRL
    hie + (1 + hfe)RE

    If RE by passed with capacitor CE, AV will increase Hence, after removing CE mid band voltage gain decreases.

    Correct Option: B


    With CE, voltage gain

    Aυ = -
    -hfeRL
    hie + (1 + hfe)RE

    If RE by passed with capacitor CE, AV will increase Hence, after removing CE mid band voltage gain decreases.


  1. If an input signal with non-zero dc component is applied to a low pass RC network, then dc component in the output will be










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    NA

    Correct Option: A

    NA



  1. A junction transistor operating at room temperature with IC = 2 mA, where (kT / q) = 20 mV and β = 100. The values of parameter gm in mhos and rπ in ohm respectively are









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    gm =
    IC
    =
    2
    = 0.08
    VT25

    rm =
    β
    =
    100
    = 1250
    gm0.08

    Correct Option: B

    gm =
    IC
    =
    2
    = 0.08
    VT25

    rm =
    β
    =
    100
    = 1250
    gm0.08