Practice MCQ on Feedback and Oscillator with Answers

**MCQ on Feedback and Oscillator with Answers**

**Q1. An amplifier has a voltage gain A _{v} = 1000, input impedance 1 kΩ and output impedance 500Ω. A fraction β_{v} = 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 f _{L} = 20 Hz and f_{H }= 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 f
_{H}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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*Answer Key* (if you find any answer wrong, feel free to Correct us)

*Answer Key*

01. | (a) | 06. | (a) | ||

02. | (c) | 07. | (c) | ||

03. | (c) | ||||

04. | (b) | ||||

05. | (b) |