An 8Ω 5.5W, 0.006% THD+N, 2×VBAT-Swing Switched-Mode Audio Amplifier with Fully-Differential Linear Buck-Boost Topology Achieving Total Efficiency of 87%

This paper presents a fully-differential single-inductor linear buck-boost power topology-based switched-mode audio amplifier. The pro-posed buck-boost topology outputs from 0 to 2× battery voltage while improving efficiency by up to 10% compared to the dual-step conversion of Class-D after the step-up. The inductor-freewheeling with a fixed de-energizing phase linearizes the voltage conversion in the buck-boost. The chip fabricated in 0.18-μm achieves 0.006% THD+N and 87% efficiency at a maximum output power of 5.5W on an 8Ω-speaker.