Oscillators are circuits that produce a continuous, repeated, and alternating waveform without using any input. They are a simple way of creating a specific frequency of a signal. In short, they work by converting unidirectional current flow from a DC source into an alternating waveform. 

Oscillators: a Description

Oscillators are amplifier circuits that have positive or regenerative feedback. These circuits have an amplifying element that can be either a transistor or an op-amp. The back-fed in-phase signal is responsible to sustain the oscillations by adjusting the losses in the circuit. When the power supply turns in, the oscillations begin due to electronic noises. As a result, these noises generate a signal that travels through a loop, gets amplified, and joins the frequency of a sine wave.

Where to Expect Them: LFOs and RFs

They are common in many electronic devices. Their main characteristic is the frequency of their output signal. On the one hand, Low-frequency oscillators (LFOs) are electronic versions that engineers employ in the field of audio synthesizers. They generate signals below 20Hz. But, in general, audio oscillators create signals between 16Hz and 20kHz. On the other, adiofrequency ones (RF) generate signals between 100kHz and 100GHz.

Types of Oscillators

There are several types and they fall into two main categories: relaxation and harmonic or linear oscillators. 

In a relaxation oscillator, the energy switches between the active and the passive components. The frequency of the oscillations is established by the charging and discharging time constants. In contrast, in a a harmonic oscillator, the energy flow switches from active components to passive ones. Moreover, the feedback path determines the frequency of the oscillations. Harmonic oscillators create low distorted sine wave outputs, whereas relaxation ones create a square, triangle or sawtooth waveforms. 

A broader classification of these circuits involves parameter features. These include the feedback mechanism, the shape of the output waveform, the frequency of the output signal, the type of frequency control, and the nature of the frequency of the output waveform.