A comparison between GaN and silicon based Class D audio power amplifiers with Pulse Density Modulation

In recent years, GaN power HEMTs are gaining acceptance in power electronic applications. However, the implementation of Class D audio power amplifiers application using GaN power HEMTs has not been widely studied. This paper studies the performance of two open-loop 25 W Class D audio power amplifiers with GaN and silicon output stages using a Pulse Density Modulation (PDM) scheme. Comparisons of the amplifier performance include distortion, efficiency and thermal effects. The GaN based amplifier shows a 0.15% reduction in distortion and an increase in efficiency of 15% at output power levels of less than 20 W. However, the GaN power output stage exhibits some performance degradation as the temperature rises.