A 2.4 mA Quiescent Current, 1 W Output Power Class-D Audio Amplifier With Feed-Forward PWM-Intermodulated-Distortion Reduction

• Published in: IEEE journal of solid-state circuits Vol. 51; no. 6; pp. 1436 - 1445
• Main Authors: Kuo, Tai-Haur, Chien, Shih-Hsiung, Huang, Jyun-Jia, Chen, Yi-Wen, Lee, Yu-An
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplification; Attenuation; class-D audio amplifier; CMOS; Distortion; low quiescent current; Mobile communication systems; MOSFET; Power generation; Pulse width modulation; PWM-intermodulated distortion; Reduction; Switching frequency; THD + N; total harmonic distortion plus noise; Tradeoffs; Transfer functions; Voltage; PWM-intermodulated distortion; low quiescent current; THD + N; total harmonic distortion plus noise; class-D audio amplifier
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2016.2543704

This work proposes a feed-forward PWM-intermodulated-distortion reduction (FFPIDR) technique for closed-loop class-D audio amplifiers. The proposed FFPIDR technique overcomes the trade-off between out-of-band loop attenuation and in-band loop gain to reduce the PWM-intermodulated distortion while maintaining a high in-band distortion suppression capability without increasing the switching frequency. This results in a high-fidelity and low-quiescent-current audio amplifier suitable for mobile devices. This work is implemented in a 0.5 μm CMOS technology, and the measurement result with a 4.2 V supply voltage shows that the proposed FFPIDR technique improves the TiD + N by 12 dB when an output power of 340 mW is delivered to an 8-Ω load. Compared with other state of the arts, the proposed class-D amplifier achieves 0.0037% TiD + N with a quiescent current of 2.4 mA and the smallest chip area of 0.86 mm 2 , and the measured peak efficiency reaches 92%.