- Electronic oscillator
An electronic oscillator is an
electronic circuitthat produces a repetitive electronic signal, often a sine waveor a square wave.
A low-frequency oscillator (LFO) is an electronic oscillator that generates an AC
waveformbetween 0.1 Hz and 10 Hz. This term is typically used in the field of audio synthesizers, to distinguish it from an audio frequency oscillator.
Oscillators designed to produce a high-power AC output from a DC supply are usually called inverters.
Types of electronic oscillator
There are two main types of electronic oscillator: the
harmonic oscillatorand the relaxation oscillator.
The harmonic oscillator produces a
sinusoidal output. The basic form of a harmonic oscillator is an electronic amplifierwith the output attached to a narrow-band electronic filter, and the output of the filter attached to the input of the amplifier. When the power supply to the amplifier is first switched on, the amplifier's output consists only of noise. The noise travels around the loop, being filtered and re-amplified until it increasingly resembles the desired signal.
piezoelectric crystal(commonly quartz) may be coupled to the filter to stabilise the frequency of oscillation, resulting in a crystal oscillator.
There are many ways to implement harmonic oscillators, because there are different ways to amplify and filter. For example:
Delay line oscillator
RC oscillator(Wien Bridge and "Twin-T")
* cross-coupled LC oscillator
relaxation oscillatoris often used to produce a non-sinusoidal output, such as a square wave or sawtooth. The oscillator contains a nonlinear component such as a transistorthat periodically discharges the energy stored in a capacitoror inductor, causing abrupt changes in the output waveform.
Square-wave relaxation oscillators can be used to provide the
clock signalfor sequential logiccircuits such as timers and counters, although crystal oscillators are often preferred for their greater stability.
Triangle-wave or sawtooth oscillators are used in the timebase circuits that generate the horizontal deflection signals for
cathode ray tubes in analogue oscilloscopes and televisionsets. In function generators, this triangle wave may then be further shaped into a close approximation of a sine wave.
Other types of relaxation oscillators include the
multivibratorand the rotary traveling wave oscillator.
Injection locked oscillator
* [http://www.howstuffworks.com/oscillator.htm Howstuffworks: oscillator] .
* [http://www.ieee.li/pdf/viewgraphs_oscillator_oddities.pdf Oscillator Oddities] .
* [http://www.ieee.li/pdf/viewgraphs_freq.pdf Tutorial on Precision Frequency Generation] .
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