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This paper presents a single chip class D audio power amplifier realized in a 0.35 mum CMOS technology. This chip consists of a high-linear single-loop feed-forward Sigma-Delta modulator with three level quantizer and a full H-bridge output stage. The three-level quantizer effectively reduces the switching activity of the output stage, especially when the input signal amplitude is low, hence improves the power efficiency. Direct feedback from H-bridge output improves the linearity of the amplifier. With a 3.3-V supply voltage and 4-Ohm load, the amplifier can deliver maximum 1-W output power with THD less than 0.8% at 8 kHz and reaches a maximum power efficiency more than 80%.