Oscillators and multivibrators are electronic circuits that are used to create repeating signals. A multivibrator can be either bistable or monostable. Oscillator is another term for an astable multivibrator. Although the two are very similar and are often used interchangeably by technicians and engineers, they have some very distinct differences.
The main difference between an oscillator and a multivibrator is the type of wave that they produce. Oscillators produce only one form of wave as its primary output, which is the basic sine wave. Multivibrators produce three types of wave, depending on the design on the multivibrator, which are the sawtooth wave, the triangle wave or the square wave. However, if a conversion circuit is added to the multivibrator, any type of basic waveform can be produced.
Oscillators have another difference in that they resonate at a specific frequency, rather than a natural frequency. An example of a natural frequency would be a bell, whereby ringing the bell produces a sound that naturally fades away. With an oscillator, however, it rings a special circuit so that the signal is created at a specific frequency. This is then sustained by an electronic amplifer, so that it never fades away. This is how the sine wave is produced by the circuit.
Quartz crystal is sometimes featured within the resonant circuit of an oscillator. This means much greater precision, due to the quartz crystal’s natural stability, and the fact that is has a resonant frequency of its own. This design is often used for watches, radios and computers as a method for obtaining precise frequency. Multivibrators generally do not incorporate quartz crystal into their circuit.
Multivibrators and oscillators also have a difference in how the switch works for producing an electronic signal. Both produce the electronic signal using this method. For an oscillator, the switch turns on when there is a low current in the circuit, which sends a charge to the capacitor. The switch turns off again when the current level is back to normal. This is then repeated. With a multivibrator, however, it remains either on or off when you switch it.