Ian Moulding
Diodes

Class D amplifiers are essentially switching amplifiers that have more in common with a switched mode power supply (SMPS) than with their linear predecessors, and now achieve a level of performance comparable to that of linear amplifiers. Class D utilizes a switching topology whereby the MOSFETs are either ON or OFF, enabling efficiencies of up to 95 percent to be achieved.

This paper explains how Class D amplifiers work and how, by processing the audio signal in the digital domain, a high level of audio signal resolution can be attained that goes some way toward achieving an ideal amplifier. The paper also discusses how sources of distortion and interference can be minimized in Class D output stages by selecting MOSFETs and gate drivers optimized for Class D applications and introducing a feedback topology to improve power supply rejection.