An oscillator circuit is an electronic circuit that generates a continuous, oscillating signal, usually in the form of a sine wave or square wave. These circuits are essential in various applications, including clocks, radios, and signal generators, as they provide a stable frequency output. Oscillator circuits can be classified into two main types: linear oscillators and non-linear oscillators. Linear oscillators, such as the Colpitts and Hartley oscillators, use reactive components like capacitors and inductors to produce oscillations. Non-linear oscillators, like the astable multivibrator, rely on feedback and switching elements to create oscillating signals.