A 118 dB PSRR, 0.00067% (-103.5 dB) THD+N and 3.1 W Fully Differential Class-D Audio Amplifier With PWM Common Mode Control

摘要

This paper presents a fully differential Class-D audio amplifier using pulse-width modulation (PWM) common-mode control to enhance the power supply rejection ratio (PSRR) and linearity. The input feed-forward technique with resistive summation is adopted in the loop filter to reduce internal swing and signal-dependent terms for further linearity enhancement. Moreover, a single amplifier biaquad (SAB) technique is utilized to reduce the number of op-amps for low-power consideration. The Class-D audio amplifier achieves a high PSRR of 118 dB for 217 Hz power supply ripples and a low total harmonic distortion plus noise (THD+N) of 0.00067% (-103.5 dB). The proposed Class-D amplifier with 1.45 mA quiescent current shows a peak SNR (A-weighted) of 108 dB, the maximum output power of 3.1 W at 1% THD+N, and 89.5% efficiency with a 4 Ω load. The Class-D audio amplifier, which occupies the active area of 1.85 mm2 in a 0.153 μ m 1P5M CMOS process, can be operated from 3 V to 5.5 V.