A filter free class D audio amplifier with 86% power efficiency

This paper presents a single chip class D amplifier with 2.5 W output power and 86% efficiency with an 8 ohm load. This chip uses a pulsed width modulation scheme that eliminates the output filter. It operates with a 2.5 V to 6.5 V supply voltage in a 7 V, 1.2 /spl mu/m, double-poly, triple-metal BiCMOS process. It has an area of 1.5 /spl times/ 1.5 mm/sup 2/ and it achieves a THD as low as 0.04%, with a flatband response between 20 Hz and 20kHz.