Question

What is an angle of phase shift for each designed RC network in the Phase Shift Oscillator circuit?

(a) 60^o

(b) 90^o

(c) 180^o

(d) 45^o

The question was posed to me during a job interview.

My doubt is from Frequency Compensation topic in chapter Frequency Response of Electronic Devices & Circuits

Answer 1

Right option is (a) 60^o

Explanation: R-C phase shift oscillator consists of three identical basic R-C phase shifting kind of networks approved in the cascade configuration.

Thus, the total phase shift introduced by three stage R-C network is equal to 180^o, which implies that the output of network leads its input by 180^o. As a result, it infers that each phase-shift stage acquires the phase shift of about 60^o.

RC network is also renowned as ‘Ladder network’. The phase-shift of about 180^o is generated particularly at one particular frequency, which is measured to be the frequency of operation of the oscillator.