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. FET tuned amplifier with gm = 5 mA/V, rd = 20 kΩ has a resonant impedance of 20 kΩ. The gain resonance is given by—








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    Given, gm = 5 mA/V, rd
    = 20 kΩ,
    Resonant impedance i.e. RD = 20 kΩ
    Now, Gain = gm (rd//RD)
    = 5 mA/V (20 kΩ//20 kΩ)
    or Gain = 5 × 10–3 × 10 × 103 = 50

    Correct Option: B

    Given, gm = 5 mA/V, rd
    = 20 kΩ,
    Resonant impedance i.e. RD = 20 kΩ
    Now, Gain = gm (rd//RD)
    = 5 mA/V (20 kΩ//20 kΩ)
    or Gain = 5 × 10–3 × 10 × 103 = 50

  1. In the circuit shown below, both transistor have the same VT. What is the approximate value of the highest possible output voltage Vout, if Vin can range from 0 to VDD? (Assume 0 < VT < VDD)










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    The given circuit

    The highest possible output of the above circuit is V0 = VDD – VT
    Where, VT is the threshold voltage and VDD supply voltage

    Correct Option: A

    The given circuit

    The highest possible output of the above circuit is V0 = VDD – VT
    Where, VT is the threshold voltage and VDD supply voltage

  1. The transconductance of (FET)1 is 100 µmho while the transconductance of (FET)2 is 50 µmho. The gate is more effective in controlling the drain current in the case of—








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    The gate is more effective in controlling the drain current in the case of (FET)1 because higher the transconductance better gate controll.

    Correct Option: A

    The gate is more effective in controlling the drain current in the case of (FET)1 because higher the transconductance better gate controll.

  1. A common source FET amplifier has Cgs = 50 pF and Cgd = 5 pF. The value of source resistance RS for high 3 dB frequency of 100 kHz will be—








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    Given, Cgs = 50 pF, Cgd = 5 pF, fT = 100 KHZ, RS =?

    We know that, fT =
    1
    2 π(Cgd + Cgs) RS

    or RS =
    1
    2 π(Cgd + Cgs) fT

    or RS =
    1
    2 × 3·14 (50 + 5) × 10–12 × 100 × 103

    or RS = 28·89 kΩ
    Hence alternative (C) is the best option.

    Correct Option: C

    Given, Cgs = 50 pF, Cgd = 5 pF, fT = 100 KHZ, RS =?

    We know that, fT =
    1
    2 π(Cgd + Cgs) RS

    or RS =
    1
    2 π(Cgd + Cgs) fT

    or RS =
    1
    2 × 3·14 (50 + 5) × 10–12 × 100 × 103

    or RS = 28·89 kΩ
    Hence alternative (C) is the best option.

  1. For the FET source follower circuit shown below, RS1 >> RS2 and transconductance gm and drain source resistance rds are 2 × 10– 3 mho and 83 K respectively. The approximately value of input and output impedance are—










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    NA

    Correct Option: C

    NA