Test: RC Phase Shift Oscillator - Electronics and Communication Engineering (ECE) MCQ

RC phase shift oscillator contains a minimum of three phase shift network. There is can be also four and it increases stability of oscillation.

One phase shift network of an RC phase shift oscillator contains one capacitor and one resistor.

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

 One phase shift network of an RC phase shift oscillator contains one capacitor and one resistor.

 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.

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.

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

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.

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

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

The frequency of oscillation is given by the equation 1/(2ᴨ√6 RC). It can be reduced as
0.65/RC.

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

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

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

 Oscillator frequency can be given by the equation