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
View Answer

Answer: b
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
View Answer

Answer: d
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
View Answer

Answer: b
Explanation: For self-oscillating circuits, the loop gain Aβ must be equal to 1, otherwise there will be the effect of noise.
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4. What is the value of input voltage, if Aβ=1 and input voltage is 5V?
a) 0
b) 2
c) 5
d) 10
View Answer

Answer: c
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
View Answer

Answer: a
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?
a) Faraday law
b) Hertz law
c) Fleming law
d) Barkhausen law
View Answer

Answer: d
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
View Answer

Answer: a
Explanation: Barkhausen criteria states that loop gain of the closed loop circuit must be equal to one in order to repeat the generation.
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8. Barkhausen criteria states phase of loop gain must be 0 for a self sustaining oscillator.
a) True
b) False
View Answer

Answer: a
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
View Answer

Answer: a
Explanation: The average value of saturation factor is equal to loop gain of the particular circuit, usually it will be nearly equal to 1.
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10. An oscillator requires an input voltage of high amplitude.
a) True
b) False
View Answer

Answer: b
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.

To practice all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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