High-efficiency dynamic supply CMOS audio power amplifier for low-power applications

This paper describes the analysis and design of a dynamic supply CMOS audio power amplifier for low-power applications. The dynamic supply technique is used to increase the efficiency of a class AB power amplifier. The polarization of its output stage is adaptive so that the maximum efficiency enhancement can be achieved without jeopardizing the linearity of the system. Two types of adaptive polarization are proposed and compared. A concept of power supplies switching is also proposed. Simulation results are presented showing that an efficiency of 53.6% at a total harmonic distortion (THD) of less than 0.1% can be achieved, whereas the maximal theoretical value for a class AB amplifier is approximately 33.3%.