RC Oscillators

Phase-shift and Wien-bridge oscillators produce low-frequency sine waves using resistors and capacitors.

Intermediate

Wien-bridge oscillator:

$f = \frac{1}{2\pi RC}$

The amplifier gain must be exactly 3; amplitude is stabilised with a lamp, thermistor or diodes in the feedback.

RC phase-shift oscillator: three RC sections give 180° phase shift, an inverting amplifier gives the other 180°:

$f = \frac{1}{2\pi RC\sqrt{6}} \quad \text{with the amplifier gain} \ge 29$

Used for audio-frequency test signals.

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