A 121.4-dB DR Capacitively Coupled Chopper Class-D Audio Amplifier

• Published in: IEEE journal of solid-state circuits Vol. 57; no. 12; pp. 3736 - 3745
• Main Authors: Zhang, Huajun, Berkhout, Marco, Makinwa, Kofi A. A., Fan, Qinwen
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplifiers; Audio power amplifier; capacitively coupled chopper amplifier; Choppers (circuits); class-D amplifier (CDA); Computer architecture; dynamic range (DR); Feedback; Gain; Harmonic distortion; Impedance matching; Jitter; noise; Signal processing; Thermal noise; Transient analysis; Wideband
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2022.3207907

This article presents a class-D amplifier (CDA) with high dynamic range (DR). To eliminate the typically dominant noise contribution of a resistive feedback network, the input and feedback signals are chopped and applied to a capacitive feedback network. However, this leads to high-voltage (HV) transients at the input of the loop filter, which, due to timing and impedance mismatch in the chopped feedback network, could degrade linearity and even overstress low-voltage (LV) core devices. Robust processing of the HV chopped feedback signal is guaranteed with chopper timing skew correction, chopper impedance matching, and deadbanding. The prototype, implemented in a 180-nm bipolar-CMOS-DMOS (BCD) process, achieves 121.4 dB of DR, 5.9 dB higher than state-of-the-art closed-loop CDAs, and 8-<inline-formula> <tex-math notation="LaTeX">\mu \text{V}_{\mathrm {RMS}} </tex-math></inline-formula> output-referred noise (A-weighted). It also achieves a peak total harmonic distortion (THD) + N of −109.8 dB and a peak efficiency of 93%/88% while driving 15 W/26 W into an 8-/4-<inline-formula> <tex-math notation="LaTeX">\Omega </tex-math></inline-formula> load.