Class-D Audio Amplifier

Characteristics

Class-D amplifiers do not amplify the analogue audio signal itself. Instead, a pulse-width modulated sine wave at the audio signal frequency is fed into a switching stage (= digital amplifier) and the high frequency part of the amplified signal is filtered out by a low pass filter.

A Class-D amplifier is therefore nothing more than a combination of a pulse width modulator (PWM) with a digital power stage and a downstream low pass filter. The block diagram shows the elements of a Class-D amplifier in full-bridge topology.