A highly efficient, 420mW class-H headphone amplifier with single power supply rail

This paper presents a new class-H audio amplifier designed for battery-powered applications. The class-H operation is implemented by an internally generated variable power supply with a fully differential class-AB amplifier. By detecting and processing the input signal, the amplifier supply voltage will be adaptively adjusted to track the instantaneous signal level and 20%-30% merit on efficiency is achieved over conventional class-AB, G amplifiers. The proposed work is realized using standard 0.18 μm CMOS technology. With a 3.3 V supply, it is capable to deliver 420 mW maximum power to the load, achieving less than 0.002% THD at 1 kHz while consuming 5.6 mW quiescent power in total.