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 transistor in the amplifier shown has following parameters: hfe = 100, hi e = 2 k Ω, hre = 0, hoe = 0.05 m mho. C is very large. The output impedance is—










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    We know the output impedance, of CE configuration in terms of h-parameter is given as

    Y0 = hoe –
    hfe·hre
    		,
    hie + RS

    where RS = source resistance
    = 0.05 × 10–3 –
    100 × 0
    2 × 103 + RS

    = 0.05 × 10–3
    or Z0 =
    1
    		=
    1
    		= 20 kΩ
    Y00.05 × 10–3

    Hence alternative (A) is the correct answer.

    Correct Option: A

    We know the output impedance, of CE configuration in terms of h-parameter is given as

    Y0 = hoe –
    hfe·hre
    		,
    hie + RS

    where RS = source resistance
    = 0.05 × 10–3 –
    100 × 0
    2 × 103 + RS

    = 0.05 × 10–3
    or Z0 =
    1
    		=
    1
    		= 20 kΩ
    Y00.05 × 10–3

    Hence alternative (A) is the correct answer.

  1. The quiescent collector current IC of a transistor is increased by changing the biasing resistance. As a result gm will—








  1. View Hint View Answer Discuss in Forum

    As we know that

    R0 =
    dV
    		,
    dIC

    on increasing quiescent collector current IC, the output resistance R0 decreases, as a result gm.
    gm = gm0 1 increases.
    R0

    Hence alternative (C) is the correct answer.

    Correct Option: C

    As we know that

    R0 =
    dV
    		,
    dIC

    on increasing quiescent collector current IC, the output resistance R0 decreases, as a result gm.
    gm = gm0 1 increases.
    R0

    Hence alternative (C) is the correct answer.

  1. Which of the following statement are correct for basic transistor amplifier configuration?










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    (A) and (B) Since CB configuration has low input impedance and low current gain and CC configuration has low output impedance and a high current gain.

    Correct Option: E

    (A) and (B) Since CB configuration has low input impedance and low current gain and CC configuration has low output impedance and a high current gain.

  1. The parameters of an FET are gm = 3 mA/V, id = 30 k. RL = 3 k as a source follower load. The output impedance is given by—








  1. View Hint View Answer Discuss in Forum

    Given that, gm = 3 mA/V, rd = 30 k, RL = 3 k, R0 =?
    We know that

    R0 =
    R'L
    1 + gmR'L

    in the case of source follower Where, R′L = RL || rd = 3 k || 30 k
    =
    3 × 30
    		≈ 3 k.
    3 + 30

    Now, R0 =
    3000
    1 + 3 × 10–3 × 3000

    =
    3000
    		 =
    3000
    		= 300 Ω
    1 + 3 × 310

    Hence alternative (D) is the correct answer.

    Correct Option: D

    Given that, gm = 3 mA/V, rd = 30 k, RL = 3 k, R0 =?
    We know that

    R0 =
    R'L
    1 + gmR'L

    in the case of source follower Where, R′L = RL || rd = 3 k || 30 k
    =
    3 × 30
    		≈ 3 k.
    3 + 30

    Now, R0 =
    3000
    1 + 3 × 10–3 × 3000

    =
    3000
    		 =
    3000
    		= 300 Ω
    1 + 3 × 310

    Hence alternative (D) is the correct answer.

  1. Given for an FET, gm = 9.5 mA/volt. Total capacitance = 500 pF. For a voltage gain of – 30 the bandwidth will be—








  1. View Hint View Answer Discuss in Forum

    Given that gm = 9.5 mA/volt, total capacitance = 500 pF, voltage gain (A0) = – 30, BW =? We know that

    A0 × BW =
    gm
    C

    where, A0 = gain
    BW = Bandwidth
    C = Total capacitance
    gm = Transconductance.
    or BW =
    gm
    A0·C

    or BW =
    9.5 × 10–3
    30 × 500 × 10–12

    or BW = 100 kHz
    Hence alternative (A) is the correct answer.

    Correct Option: A

    Given that gm = 9.5 mA/volt, total capacitance = 500 pF, voltage gain (A0) = – 30, BW =? We know that

    A0 × BW =
    gm
    C

    where, A0 = gain
    BW = Bandwidth
    C = Total capacitance
    gm = Transconductance.
    or BW =
    gm
    A0·C

    or BW =
    9.5 × 10–3
    30 × 500 × 10–12

    or BW = 100 kHz
    Hence alternative (A) is the correct answer.