A Chopper Class-D Amplifier for PSRR Improvement Over the Entire Audio Band

A Chopper Class-D Amplifier for PSRR Improvement Over the Entire Audio Band

Zhang, H. (TU Delft Electronic Instrumentation)
Rozsa, N.N.M. (TU Delft Electronic Instrumentation)
Berkhout, Marco (Goodix Technologies)
Fan, Q. (TU Delft Electronic Instrumentation)

2022

The power supply rejection ratio (PSRR) of conventional differential closed-loop Class-D amplifiers is limited by the feedback and input resistor mismatch and finite common-mode rejection ratio (CMRR) of the operational transconductance amplifier (OTA) in the first integrator. This article presents a 14.4-V Class-D amplifier employing chopping to tackle the mismatch, thereby improving the PSRR. However, chopping-induced intermodulation (IM) within a pulsewidth modulation (PWM)-based Class-D amplifier can severely degrade PSRR and linearity. Techniques to mitigate such IM are proposed and analyzed. To chop the 14.4-V PWM output signal, a high-voltage (HV) chopper employing double-diffused MOS (DMOS) transistors is developed. Its timing is carefully aligned with that of the low-voltage (LV) choppers to avoid further linearity degradation. The prototype, fabricated in a 180-nm BCD process, achieves a PSRR of >110 dB at low frequencies, which remains above 79 dB up to 20 kHz. It achieves a total harmonic distortion (THD) of -109.1 dB and can deliver a maximum of 14 W into an 8- \Omega load with 93% efficiency while occupying a silicon area of 5 mm2.

Audio power amplifier
Class-D amplifier
intermodulation (IM)
power supply rejection ratio (PSRR)
total harmonic distortion (THD).

http://resolver.tudelft.nl/uuid:743f3859-5920-4a19-a2c1-1d7f45599c37

https://doi.org/10.1109/JSSC.2022.3161136

0018-9200

IEEE Journal of Solid State Circuits, 57 (7), 2035 - 2044

Accepted Author Manuscript

Institutional Repository

journal article

© 2022 H. Zhang, N.N.M. Rozsa, Marco Berkhout, Q. Fan