Class C

Definition

A class C amplifier is a form of switching amplifier in which the transistors are on for less than a half cycle (less than 180 degrees) -- often, much less.

For instance, the transistor may be on only during the top 10% of the signal excursion, delivering just a pulse.

Class C amps are very efficient because the transistors are off most of the time and when they are on, they are in full conduction. They deliver high distortion and are often used in RF circuits, where tuning circuits restore some of the original signal and reduce distortion. They are also used in low-fidelity applications where the distortion is not important, such as a siren speaker driver.