Design of a power-efficient and high fidelity class-D amplifier

Abstract

This Final Year Project (FYP) pertains to a mid-power (20W, 20V) analog Class D power amplifier for audio applications. Power amplifier is usually the most power consuming block in an audio system and in some applications, the power consumption of the power amplifier is >70% of the overall power dissipation. Therefore it is imperative that the power-efficiency of the power amplifier be high.

In this project, the overall objective is to design and realize a mid-power (20W, 20V) analog Class D amplifier with emphasis on high power-efficiency. To improve the overall power efficiency of the Class D amplifier, in this project, Gallium Nitride (GaN) transistors are employed in the output stage. Compared to conventional Class D amplifier whose output stage is silicon transistors (such as LDMOS), the switching power of the Class D output is significantly reduced, by >50%. This is because the parasitic capacitance of GaN transistors is significantly smaller than that of silicon transistors for the same output impedance. The significantly reduced capacitance subsequently results in reduced switching power dissipation (hence reduced overall power dissipation).