A 0.0004% (−108dB) THD+N, 112dB-SNR, 3.15W fully differential Class-D audio amplifier with Gm noise cancellation and negative output-common-mode injection techniques

Flicker (1/f) noise is a main design issue when realizing a low-noise and high-SNR audio amplifier. Utilizing large device sizes and chopper-stabilization techniques are commonly adopted approaches to mitigate 1/f noise. However, the choppers are seldom used in pulse-width-modulation (PWM) Class-D audio amplifiers (CDAs) because the conventional chopping method applied in the opamps along the signal path of CDAs inevitably results in extra aliasing and deteriorates the linearity. Therefore, a CDA with high SNR and low total harmonic distortions (THDs) has become a challenging design to ensure high-fidelity audio applications.