A Small Signal Model of the Design of a Class D Power Switching Amplifier

The class D amplifier is not well known in audio applications. Its excellent power ratio (greater than 90%) is the most important advantage. The MOS transistors switching power stage is able to drive a useful power up to 100W to the loud speaker. However, designing such an amplifier is more difficult than designing a classical class A or AB power amplifier. The distortion level is also slightly higher than in AB structures. Despite the abundant knowledge on class D, there was no electronic model available till now. Then, a small signal model is présentented to make the design as simple as possible. The experimental results are given to illustrate the design method.