RC Oscillator Frequency

f = 1 / (2πRC)

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Result
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Formula

f = 1 / (2πRC)

Description

RC oscillators use resistors and capacitors to generate periodic waveforms without inductors. The simplest forms include the phase-shift oscillator (three RC stages providing 180 degrees phase shift) and the Wien bridge oscillator (using a series-parallel RC network). The oscillation frequency is determined by the RC time constant. RC oscillators are easy to build and tune but have lower frequency stability than crystal oscillators, making them suitable for audio frequencies and non-critical timing applications. Op-amp-based Wien bridge oscillators can produce clean sine waves from a few Hz to several hundred kHz.

Variables

  • f — Oscillation frequency (Hz)
  • R — Resistance (Ω)
  • C — Capacitance (F)

Practical Notes

The Wien bridge oscillator needs automatic gain control (AGC) to maintain stable amplitude. A classic technique uses a small incandescent lamp as a positive temperature coefficient element in the feedback network. Modern implementations use JFETs or analog multipliers for AGC. For best frequency stability, use NP0/C0G ceramic or film capacitors and metal film resistors.

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