# Analog Circuits Questions and Answers – RC Phaseshift Oscillator

This set of Basic Analog Circuits Questions and Answers focuses on “RC Phaseshift Oscillator”.

1. RC phase shift oscillators contain a minimum of _________ Phase shift network.
a) 1
b) 2
c) 3
d) 0

Explanation: RC phase shift oscillator contains a minimum of three phase shift networks. There can be also four and it increases the stability of oscillation. They yield a pure sine wave for a variety of loads.

2. One phase shift network of an RC phase shift oscillator contain __________ capacitor.
a) 1
b) 2
c) 3
d) 0

Explanation: One phase shift network of an RC phase shift oscillator contains one capacitor and one resistor. This single network causes a phase shift of 60° and a total of 180° through the amplifier stage and 180° through the second inverting stage, a total of 0.

3. One phase shift network of an RC phase contain _________ inductor.
a) 1
b) 2
c) 3
d) 0

Explanation: One phase shift network of an RC phase shift oscillator contains one capacitor and one resistor. There is no need of an inductor.

4. One phase shift network of an RC phase contain __________ resistor.
a) 1
b) 2
c) 3
d) 0

Explanation: One phase shift network of an RC phase shift oscillator contains one capacitor and one resistor. This single network causes a phase shift of 60° and a total of 180° through the amplifier stage and 180° through the second inverting stage, a total of 0.

5. Phase shift provided by one phase shift network in RC phase shift oscillator in 3 stage is ___________
a) 180 degrees
b) 60 degrees
c) 120 degrees
d) 90 degrees

Explanation: Phase shift provided by one phase shift oscillator in RC phase shift oscillator in 3 stage is 60 degrees. It is 180/number of stages.
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6. Total phase shift provided by all phase shift networks in RC phase shift oscillator is ___________
a) 180 degrees
b) 60 degrees
c) 120 degrees
d) 360 degrees

Explanation: To satisfy Barkhausen’s criteria total phase shift should be 360 degrees. 180 degrees is produced by amplifier and rest by phase shift network even it is three stage or four stage.

7. The phase shift network will produce a phase shift of 180 degrees at ___________
a) Three different frequencies
b) One frequency
c) Two different frequencies
d) Infinitely many frequencies

Explanation: The phase shift oscillator will produce a phase shift of 180 degrees only at a particular frequency by which it is meant to oscillate.

8. Which of the following is not a reason for beginning oscillations in RC phase shift oscillator?
a) Phase shift network
b) Noise inherent in transistor
c) Minor variations in the voltage DC source
d) Square wave signal

Explanation: Phase shift network doesn’t initialize the oscillation it just phase shift a given frequency. Oscillation will start by noise inherent of transistor or by minor voltage variations in DC source.

9. Amplifier gain for RC phase shift oscillation, to obey Barkhausen’s criteria should be minimum of ___________
a) 43
b) 4
c) 10
d) 29

Explanation: Amplifier gain should be a minimum of 29 or else Aβ will be less than one.

10. Phase shift provided by one phase shift network in RC phase shift network in 4-stage will be ___________
a) 180 degrees
b) 45 degrees
c) 60 degrees
d) 90 degrees

Explanation: Phase shift provided by one phase shift oscillator in RC phase shift oscillator in 4 stage is 45degrees. It is 180/number of stages.

11. Frequency of oscillation for three section RC phase shift network is given by ___________
a) 1/(ᴨ√6 RC)
b) 2/(ᴨ√6 RC)
c) 1/(2ᴨ√6 RC)
d) 1/(2√6 RC)

Explanation: For an RC phase shift oscillator the frequency formula is 1/2πRC√2N where N is the total number of RC stages. For a 3 stage circuit, the frequency is 1/2πRC√6.

12. Distortion level in the output of RC phase shift network will be less than ___________
a) 1%
b) 2%
c) 5%
d) 10%

Explanation: Distortion in the output of phase shift oscillator is less 5%.

13. Which of the following is not true for an RC phase shift oscillator?
a) Not Bulky
b) Less costly
c) Effective for oscillation less than 10KHz
d) Pure sine wave output is possible

Explanation: Since only one frequency can fulfill barkhausen’s criteria requirement positive feedback occurs only for one frequency. Hence pure sine wave is not possible.

14. The feedback factor for RC phase shift oscillator is ___________
a) 1/18
b) 1/29
c) 1/11
d) 1/33

Explanation: The feedback factor for RC phase shift oscillator is 1/29 and to satisfy Barkhausen’s criteria amplifier gain should be greater than 29.

15. What will be oscillator frequency, if phase shift network of 3stages of RC phase shift oscillator contains a capacitor of 7nF and a resistance of 10K in each stage?
a) 928 Hz
b) 1KHz
c) 1.2KHz
d) 895Hz

Explanation: Oscillator frequency can be given by the equation .

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