oscillator, electronic

oscillator, electronic

(ŏs`əlā'tər), electronic circuit that produces an output signal of a specific frequency. An oscillator generally consists of an amplifieramplifier,
device that accepts a varying input signal and produces an output signal that varies in the same way as the input but has a larger amplitude. The input signal may be a current, a voltage, a mechanical motion, or any other signal; the output signal is usually of the
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 having part of its output returned to the input by means of a feedbackfeedback,
arrangement for the automatic self-regulation of an electrical, mechanical, or biological system by returning part of its output as input. A simple example of feedback is provided by a governor on an engine; if the speed of the engine exceeds a preset limit, the
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 loop; the necessary and sufficient condition for oscillation is that the signal, in passing from input to output and back to input via the feedback loop, arrive at the input with no change in amplitude or phase. If this condition is met for only a single frequency, the output is a pure sine wave; if it is met for more than one frequency, the output is a complex wave. Some oscillators are designed to operate under certain conditions so that the output is a square wave, a triangular wave, or a pulse. In some cases, a very stable mechanical oscillator, such as a specially prepared quartz crystal, may be coupled to an electronic oscillator to enhance its frequency stability. The frequency of a voltage-controlled oscillator, used in frequency modulationmodulation,
in communications, process in which some characteristic of a wave (the carrier wave) is made to vary in accordance with an information-bearing signal wave (the modulating wave); demodulation is the process by which the original signal is recovered from the wave
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, is automatically adjusted by a small control current.
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