Through the use of IR’s Class D audio chipsets, class D audio amplifiers are achieving superior efficiency and audio quality in today’s audio market. To optimize the performance of class D audio amplifiers, designers should be diligent in designing the schematic, selecting appropriate components, and laying out the PCB (printed circuit board). While the first 2 steps have well established guidelines for design, the layout of a class D amplifier remains the most obscure part of the design process. The purpose of this application note is to highlight aspects of the PCB layout which require a designer’s careful attention.
Class D audio amplifiers can be separated into 2 stages – the gate driving stage and the output stage. Each stage is characterized by specific current loops, components, and common impedances that influence the quality of the amplification. In understanding the composition of each stage, PCB designers can proceed to layout a class D audio amplifier with optimized performance and efficiency.