FEEDBACK AMPLIFIER

Objective Questions

Short notes

Objective questions (Answers are given below)

  1. The advantage of using negative feedback in an
    amplifier is that its gain can be made practically
    independent of
    (a) temperature changes
    (b) age of components
    (c) frequency
    (d) all of the above
  1. Feedback in an amplifier always helps to
    (a) control its output
    (b) increase its gain
    (c) decrease its input impedance
    (d) stabilize its gain.
  2. The only drawback of using negative feedback
    in amplifiers is that it involves
    (a) gain sacrifice
    (b) gain stability
    (c) temperature sensitivity
    (d) frequency dependence.
  3. Closed-loop gain of a feedback amplifier is the
    gain obtained when
    (a) its output terminals are closed
    (b) negative feedback is applied
    (c) feedback loop is closed
    (d) feedback factor exceeds unity.
  4. A large sacrifice factor in a negative feedback
    amplifiers leads to
    (a) inferior performance
    (b) increased output impedance
    (c) characteristics impossible to achieve without
    feedback
    (d) precise control over output.
  5. Negative feedback in an amplifier
    (a) lowers its lower 3 dB frequency
    (b) raises its upper 3 dB frequency
    (c) increases its bandwidth
    (d) all of the above.
  6. Regarding negative feedback in amplifiers which
    statement is WRONG ?
    (a) it widens the separation between 3 dB
    frequencies
    (b) it increases the gain-bandwidth product
    (c) it improves gain stability
    (d) it reduces distortion.
  7. Negative feedback reduces distortion in an amplifier
    only when it
    (a) comes as part of input signal
    (b) is part of its output
    (c) is generated within the amplifier
    (d) exceeds a certain safe level.
  8. An amplifier with no feedback has a gain-bandwidth
    product of 4 MHz. Its closed-loop gain is
  9. The new band-width is
    (a) 100 kHz
    (b) 160 MHz
    (c) 10 MHz
    (d) 20 kHz.
  10. The shunt-derived series-fed feedback in an amplifier
    (a) increases its output impedance
    (b) decreases its output impedance
    (c) increases its input impedance
    (d) both (b) and (c).
  11. A feedback amplifier has a closed gain of –200.
    It should not vary more than 50% despite 25%
    variation in amplifier gain A without feedback.
    The value of A is
    (a) 800
    (b) – 800
    (c) 1000
    (d) –1000
  12. The gain of a negative feedback amplifier is
    40 dB. If the attenuation of the feedback path is
    50 dB, then the gain of the amplifier without
    feedback is
    (a) 78.92
    (b) 146.32
    (c) 215.51
    (d) 317.23
  1. (d) 2. (a) 3. (a) 4. (c) 5. (c) 6. (d) 7. (b) 8. (c) 9.(a) 10. (d) 11. (d) 12. (b) 13. (b)

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