Physical electronics devices and ics miscellaneous

Physical electronics devices and ics miscellaneous

Easy Questions

Physical Electronics Devices and ICs

Physical electronics devices and ics miscellaneous
  1. The early effect in a bipolar junction transistor is caused by—








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    The early effect in a bipolar junction transistor is caused by large collector-base reverse bias.

    Correct Option: C

    The early effect in a bipolar junction transistor is caused by large collector-base reverse bias.

  1. In a transistor amplifier, the reverse saturation current I0 is—








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    In a transistor amplifier, the reverse saturation current I0 is doubled for every 10°C rise in temperature.

    Correct Option: A

    In a transistor amplifier, the reverse saturation current I0 is doubled for every 10°C rise in temperature.

  1. The approximate value of input impedance of a common emitter amplifier with emitter resistance Re is given by—








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    The equivalent h-parameter model of a common emitter amplifier with emitter resistance Re is given by: (i.e., fig-1)
    however the approximate h-parameter model is given by (i.e., fig-2)
    From above figure the approximate value of input impedance.

    Ri =
    Vi
    ib

    Applying KVL in the input loop, we get
    Vi – hie ib – i e Re = 0
    or Vi/ – hie ib – (i b + i c) Re = 0
    or Vi – hie ib – (i b + hfeib) Re = 0 or Vi = [hie + (1 + hfe) Re] i b
    or =
    Vi
    		= Ri = hie + (1 + hfe) Re
    ib

    Hence alternative (B) is the correct choice.


    Correct Option: B

    The equivalent h-parameter model of a common emitter amplifier with emitter resistance Re is given by: (i.e., fig-1)
    however the approximate h-parameter model is given by (i.e., fig-2)
    From above figure the approximate value of input impedance.

    Ri =
    Vi
    ib

    Applying KVL in the input loop, we get
    Vi – hie ib – i e Re = 0
    or Vi/ – hie ib – (i b + i c) Re = 0
    or Vi – hie ib – (i b + hfeib) Re = 0 or Vi = [hie + (1 + hfe) Re] i b
    or =
    Vi
    		= Ri = hie + (1 + hfe) Re
    ib

    Hence alternative (B) is the correct choice.


  1. Thermal runaway in a transistor biased in the active region is due to—








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    Thermal runaway in a transistor biased in the active region is due to change is reverse saturation current due to rise in temperature.

    Correct Option: D

    Thermal runaway in a transistor biased in the active region is due to change is reverse saturation current due to rise in temperature.

  1. From a measurement of the rise time of the output pulse on an amplifier whose input is a small amplitude square wave, one can estimate which of the following parameter of the amplifier?








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    NA

    Correct Option: C

    NA