Circuit Diagram:
Explanation: Here the collector resistor RC limits the collector current of the transistor, resistors R1 and R2 form the voltage divider network while the emitter resistor RE improves the stability. Next, the capacitors CE and Co are the emitter by-pass capacitor and the output DC decoupling capacitor, respectively. Further, the circuit also shows three RC networks employed in the feedback path. This RC networks causes the output waveform to shift by 180° during its course of travel from output terminal to the base of the transistor. Next, this signal will be shifted again by 180° by the transistor in the circuit due to the fact that the phase-difference between the input and the output will be 180° in the case of common emitter configuration. This makes the net phase-difference to be 360°, satisfying the phase-difference condition.
Circuit diagram of RC phase shift oscillator:
WORKING: * Circuit consists of a single stage amplifier in common emitter configuration & RC phase shifting network. * R1, R2, RE provides biasing & CE is bypass capacitor. * Common emitter amplifier introduces a 1800 phase shift between input & output. & remaining 1800 phase shift is produced by three identical basic RC phase shifting networks. * Each RC network is designed to introduce a phase shift of 600 . * The phase shift around the loop is 3600 only at one precise frequency.