An oscillator is an electronic circuit that produces a periodic, oscillating or alternating current (AC) signal, usually a sine wave, square wave or a triangle wave, powered by a direct current (DC) source. Oscillators are found in many electronic devices, such as radio receivers, television sets, radio and television broadcast transmitters, computers, computer peripherals, cellphones, radar, and many other devices. They are essential components that produce a periodic electronic signal, typically a sine wave or square wave, and convert DC signal to periodic AC signals which can be used to set frequency, be used for audio applications, or used as a clock signal.
There are many types of electronic oscillators, but they all operate according to the same basic principle: a feedback oscillator circuit consists of two parts connected in a feedback loop with its output fed back into its input through a frequency selective electronic filter to provide positive feedback. When the power supply to the amplifier is switched on initially, electronic noise in the circuit provides a non-zero signal to get oscillations started. An oscillator can be designed so that the oscillation frequency can be varied over some range by an input voltage or current. These voltage-controlled oscillators are widely used in phase-locked loops, in which the oscillators frequency can be locked to the frequency of another oscillator.
Some common types of electronic oscillators include:
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RC Oscillator: A type of feedback oscillator which is built using resistors and capacitors, along with an amplifying device such as a transistor or operational amplifier.
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LC or Inductor-Capacitor Oscillator: A type of oscillator which utilizes a tank circuit to produce positive feedback for sustaining oscillation. The schematic contains an inductor, capacitor, and also an amplifying component.
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Tuned Collector Oscillator: A transformer and a capacitor connected in parallel and switched with a transistor. This circuit is the most basic LC oscillator.
The frequency at which an oscillator works is usually determined by a quartz crystal. When a direct current is applied to such a crystal, it vibrates at a frequency that depends on its thickness, and on the manner in which it is cut from the original mineral rock. However, the best stability (constancy of frequency) is obtained in oscillators that use quartz crystals. The signal produced by an electronic oscillator can be viewed using a piece of equipment called an oscilloscope, which displays the signal on a screen where the y-axis represents voltage and the x-axis represents time.
