Phase-shift oscillator

[2] This schematic drawing shows the oscillator using a common-emitter connected bipolar transistor as an amplifier.

The two resistors R and three capacitors C form the RC phase-shift network which provides feedback from collector to base of the transistor.

The implementation of the phase-shift oscillator shown in the diagram uses an operational amplifier (op-amp), three capacitors and four resistors.

The single op-amp circuit needs a relatively high gain (about 30) to maintain the oscillation due to the RC sections loading each other.

An isolated version of the oscillator can be made by inserting an op-amp buffer between each RC stage (this also simplifies the modeling equations).