MCQ on Feedback and Oscillator with Answers

Practice MCQ on Feedback and Oscillator with Answers

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MCQ on Feedback and Oscillator with Answers

Q1. An amplifier has a voltage gain Av = 1000, input impedance 1 kΩ and output impedance 500Ω. A fraction βv = 0.1 of the output voltage is fed back in the serie in opposition to the input voltage. The input and output impedance after the feedback are given respectively by the approximate values.

  • (a) 100 kΩ and 5 kΩ
  • (b) I kΩ and 5 kΩ
  • (c) 10 kΩ and 50 kΩ
  • (d) 100 kΩ and 100 kΩ

Q2. An amplifier of gain 1000 is made into a feedback amplifier by feeding 9.9%% of its output voltage n series with the put opposing. If fL = 20 Hz and fH = 200 kHz for the amplifier without feedback, then due to the feedback.

  • (a) The gain decrease by 10 times
  • (b) The output resistance increases by 10 times
  • (c) The fH increases by 100 times
  • (d) The input resistance decreases by 100 times.

Q3. An amplifier has a 40 dB gain. Its gain may change by 10 % due to change in its parameters. Negative feedback is used to reduce this change only to 1%. Then the value of feedback factor B is

  • (a) β = 0.1
  • (b) β = 10
  • (c) β = 0.09
  • (d) β = 0.001

Q4. An amplifier with negative feedback has a voltage gain of 100. It is found that with feedback an input signal of 0.6 V is required to produce a given output whereas without feedback the input signal must be only 30 m\ for the same output. Then the voltage gain without feedback A and feedback factor β arc A.

  • (a) A=1000, β = 9/1000
  • (b) A=1000, β = 10/1100
  • (c) A=1000, β = 13/1200
  • (d) A=1000, β = 11/1200

Q5. The input impedance of an amplifier increases by the introduction of feedback. It is due to

  • (a) positive feedback
  • (b) current series negative feedback
  • (c) current shunt negative feedback
  • (d) voltage shunt negative feedback

Q6. In a RC coupled amplifier, the reduction in voltage gain in the high frequency range results due to:

  • (a) coupling capacitor
  • (c) series capacitance in the circuit
  • (6) shunt capacitance n the circuit
  • (d) bypass capacitor in the inner circuit

Q7. In a amplifier the negative feedback is a process where a portion of output signal is ted to the input of the normal amplifier with the condition that the input signal is:

  • (a) in phase
  • (b) 90° out of phase
  • (c) 180° out of phase
  • (d) any arbitrary phase

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