# Electronic Devices and Circuits Questions and Answers – Oscillators – 1

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Oscillators – 1”.

1. What are oscillators?
a) Switching circuits
b) Converts dc to ac
c) Converts ac to dc
d) Filter circuits

Explanation: Oscillator circuits are the one which uses dc power supply and converts it to alternating sinusoidal signals.

2. Give the relation between output and input voltage of an oscillator?
a) Av = Vi/Vo
b) Vi = Vo Av
c) Vo = Av/Vi
d) Av = Vo/Vi

Explanation: For an oscillator circuit the output voltage is the product of input voltage and gain of an amplifier.

3. What is the value of self-oscillating circuits?
a) 0
b) 1
c) 2
d) 3

Explanation: For self-oscillating circuits, the loop gain Aβ must be equal to 1, otherwise there will be the effect of noise.

4. What is the value of input voltage, if Aβ=1 and input voltage is 5V?
a) 0
b) 2
c) 5
d) 10

Explanation: since Aβ =1, it is a self oscillating circuits and hence output always has the peak amplitude of 5V.

5. For an oscillator, input voltage is 5V, loop gain is 2, find output voltage?
a) 10
b) 20
c) 5
d) 15

Explanation: For an oscillator, the output voltage is the product of loop gain and input voltage, hence output will be twice the input, that is 5*2 =10V.

6. For practical oscillators, which law has to be obeyed?
b) Hertz law
c) Fleming law
d) Barkhausen law

Explanation: For an oscillator circuit, it has to obey the Barkhausen criteria, otherwise the output f the oscillator will tend to zero as the time advances.

7. Which of the following expression depicts Barkhausen criteria?
a) Aβ = 1
b) Aβ = 0
c) Aβ < 1 < Aβ
d) Aβ < 1

Explanation: Barkhausen criteria states that loop gain of the closed loop circuit must be equal to one in order to repeat the generation.

8. Barkhausen criteria states phase of loop gain must be 0 for a self sustaining oscillator.
a) True
b) False

Explanation: For an oscillator circuit, the phase of loop gain must be equal to zero or integral multiple of 2nπ.

9. What is the average value of saturation factor in a practical circuit?
a) 1
b) 0
c) 2
d) 3

Explanation: The average value of saturation factor is equal to loop gain of the particular circuit, usually it will be nearly equal to 1.

10. An oscillator requires an input voltage of high amplitude.
a) True
b) False

Explanation: An oscillator circuit does not require an input voltage, an oscillator can be designed without giving an input signal.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

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