Electronic oscillator

An electronic circuit that generates a repeating electrical signal, typically by feeding part of its output back to sustain oscillation.

Positive feedback: A feedback process in which returned output reinforces the input that produced it. Oscillators use reinforcing feedback to replace energy lost each cycle.
LC circuit: A circuit combining an inductor and capacitor to exchange energy and resonate. Its resonant frequency sets the output of many radio-frequency oscillators.
Voltage-controlled oscillator: An oscillator whose output frequency varies with an applied control voltage. Voltage tuning lets a circuit track channels and implement frequency modulation.
Electronic amplifier: A circuit that increases the amplitude or power of an input signal. An amplifier needs an input; an oscillator creates a periodic output without one.
Barkhausen criterion: A condition for sustained sinusoidal oscillation requiring unity loop gain and a net phase shift of an integer multiple of 360 degrees. It gives the familiar loop-gain test for oscillation at a circuit’s frequency.
RC circuit: A circuit combining resistors and capacitors, often used to shape timing and frequency-dependent phase shifts. RC networks provide frequency selection without inductors in low-frequency designs.
Phase-locked loop: A feedback system that adjusts an oscillator to maintain a chosen phase relationship with a reference signal. It stabilizes or tunes an oscillator by comparing its output with a reference.
Multivibrator: A circuit that switches among states to produce rectangular or pulse waveforms. It is a broad switching-circuit family that includes relaxation oscillators.
Resonance: A response peak that occurs when a system is driven near one of its natural frequencies. Resonant networks select the frequency that an oscillator reinforces.
Crystal oscillator: An oscillator whose frequency is controlled by the mechanical resonance of a piezoelectric crystal. A quartz crystal provides a sharply defined frequency for stable timing.

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