Until recently, to achieve high-quality sound from an audio amplifier cost thousands of dollars and relied on a large, heavy, power-hungry class-A amplifier. Now, the advent of gallium nitride FETs and ICs is ushering the age of high quality, lower cost class-D audio amplifiers. 

Distortion Performance Issues Lowered with GaN

Historically, meeting the required distortion performance targets (THD+N, TIM and IM) for high-quality audio, class-D amplifiers had to resort to incorporating large amounts of feedback circuitry to compensate for poor open-loop performance. The source of this distortion was the silicon power MOSFET.

Efficient Power Conversion (EPC) is doubling the performance distance between the aging silicon power MOSFET and eGaN® transistors with 200 V ratings.  The new fifth-generation devices are about half the size of the prior generation.  This performance boost comes from two main design differences, as shown in figure 1.  On the left is a cross-section of the fourth generation 200 V enhancement-mode GaN-on-Si process.  The cross-section on the right is the fifth-generation structure with reduced distance between gate and source electrodes and an added thick metal layer. These improvements, plus many others not shown, have doubled the performance of the new-generation FETs.