Subject: Liner Integrated Circuits

Topic: Applications of Operational Amplifier

Difficulty: Low

RC Phase Shift Oscillator

A 3-stage RC Phase Shift Oscillator is required to produce an oscillation frequency of 5kHz.

R = 0.065 / (fo x C)

Assume C = 0.01uF
R = 0.065 / (5K x 0.01uF)
=1300
= 1.2K (standard)

To prevent the loading of the amplifier because of RC networks, it is necessary that R1 >= 10 R.
therefore R1 = 12K

Since the resistor-capacitor combination in the RC Oscillator circuit also acts as an attenuator producing a total attenuation of -1/29th ( Vo/Vi = β ) across the three stages, the voltage gain of the amplifier must be sufficiently high enough to overcome these RC losses

Av >29
Av = Rf / R1

if R1 = 12K
Rf = 29 x 12K
= 340K