A Low-EMI, High-DR Class-D Audio Amplifier With Double-Sided V oltage-Boosting Modulation Jhuang-Wei Cyue

Abstract

This article presents a digital-input class-D audio amplifier (CDA) that employs a double-sided voltage-boosting (DSVB) modulation scheme, integrating a capacitively coupled chopper amplifier (CCCA) with a single-inductor buck–boost power stage. The CCCA achieves a high dynamic range (DR) due to its very low noise floor and is implemented with common low-voltage (LV) input devices, while the voltage-boosting power stage achieves a boosted output power ( POUT) with good power efficiency due to its single-stage power delivery. Compared with prior-art CDAs utilizing a capacitive-feedback scheme with two off-chip inductors, this work uses only a single o ff-chip induc- tor and has additional output voltage ( VOUT) boost capability. The proposed DSVB modulation doubles the e ffective switching frequency to enhance the LC attenuation, leading to reduced differential-mode electromagnetic interference (EMI) and, unlike typical BD modulation, no modulation-induced common-mode EMI is generated. Compared with the other state-of-the-art LV digital-input CDAs, this work’s CDA, fabricated using a 0.5- µm process, achieves the highest DR of 121.3 dB and peak signal-to- noise ratio (PSNR) of 115 dB, as well as a competitive minimal total harmonic distortion plus noise (THD +N) of 0.0019%. It can deliver a maximum POUT of 1.6 W into an 8- Ω load with a peak power efficiency of 87.2%.