Let an amp having gain A and a feedback path having gain β (amount of output feedback to input). Then for this system to oscillate the loop gain AB must satisfy the condition Aβ = 1, known as Barkhausen criteria.
An oscillator is a device that generate a periodic ac output signal without any form of input signal required. The term is usually used in the context of a sine wave signal generator, while a square wave generator is usually called a multivibrator. These oscillators re used in laboratory for producing sine, square, triangular wave with amplitudes and frequencies that can be adjusted thus has a great significance.
Wein bridge oscillator:
The circuit diagram of Wein bridge oscillator is as shown in figure.
This note is based on MSC physics, Nepal.