A Low Quiescent Current, Low THD+N Class-D Audio Amplifier With Area-Efficient PWM-Residual-Aliasing Reduction

An area-efficient pulsewidth modulation (PWM)-residual-aliasing reduction technique is proposed for Class-D audio amplifiers by utilizing a low-complexity feed-forward path to cancel the PWM high-frequency components inside the feedback loop. The proposed technique reduces the PWM-residual-aliasing distortion without increasing the required switching frequency or power-hungry controller circuits, thereby lowering both the quiescent current and total harmonic distortion plus noise (THD+N) in Class-D audio amplifiers. Measurement results show that the proposed technique improves the THD+N of second-order Class-D amplifiers by 16.2 dB with a 1-kHz input; in addition, the Class-D amplifier of this paper achieves a minimum THD+N of 0.0032% while operating at a 215-kHz switching frequency, resulting in a reduction in quiescent current of more than 33%. Compared with other state of the arts, this paper implemented in 0.5-μm CMOS technology features a competitive THD+N while consuming the lowest quiescent current of 0.96 mA and occupying the smallest active area of 0.49 mm
²
.