Class D: Amplifier principle: 90% of the delivered Performance is made available to the speakers and not converted into heat.
A Class-D circuit can be divided into three areas:
The first area consists of the input for the audio signal, a (triangular) Signalgenerator and a so-called comparator (Comp). The actual switching gain stage consists of a controller and the transistors (usually MOSFETs) that amplify the PWM signal coming from the comparator.
The low pass-Filter (high frequencies are filtered out, see impedance), which the signal generated at the input (the carrier frequency) is filtered out again.