Band Separation and Efficiency Optimization in Linear-Assisted Switching Power Amplifiers

Linear-assisted switching power amplifiers are based on combinations of switching converters (for high efficiency) and linear amplifiers (for high-speed, wide bandwidth responses) in applications such as envelope tracking for RF power amplifiers in polar modulation architectures, or audio amplifiers. This paper describes an approach to band separation and filter design to maximize the system efficiency and achieve near-ideal, wide-bandwidth responses. An experimental prototype is described, including a synchronous buck converter in combination with a class-AB linear amplifier. Experimental results for square wave and rectified sinusoid input signals demonstrate high bandwidth and high efficiency of the linear-assisted switching power amplifiers with optimized band separation.