RC Phase Shift Oscillator using Op-Amp

The RC Phase Shift Oscillator using Op-Amp is a classic analog circuit designed to generate a continuous sinusoidal waveform without requiring any external input signal. At its core, the circuit uses an operational amplifier configured as an inverting amplifier. The op-amp provides the necessary voltage gain to sustain oscillation, while introducing an automatic 180-degree phase shift between its input and output. To achieve the total 360-degree phase shift required for positive feedback and sustained oscillation at a specific frequency, a feedback network composed of three identical resistor-capacitor (RC) stages is connected between the op-amp output and its inverting input. Each individual RC stage introduces a frequency-dependent phase shift. By cascading three identical stages using the specified 100kΩ resistors and 100pF capacitors, the network achieves an additional 180-degree phase shift at the frequency of oscillation, perfectly complementing the inversion introduced by the op-amp. Resistors such as the 10kΩ and 4.7kΩ components are used to set the proper DC biasing and gain parameters around the LM741 op-amp, ensuring that the loop gain satisfies the Barkhausen criterion—meaning the gain is precisely unity at the oscillation frequency. As power is applied, ambient electrical noise is amplified, and the selective feedback network ensures that only a single frequency builds up into a stable, clean sine wave. An oscilloscope can be connected to the output terminal to visually monitor, measure, and analyze the resulting waveform's frequency and amplitude.