An Integrated 3-Level Fully Adjustable PWM Class-D Audio Amplifier in 0.35μm CMOS

A class-D audio amplifier utilizing a fully adjustable 3-level pulse width modulation (PWM) is presented. The amplifier is fully integrated in a 0.35 μm CMOS process, and is powered by a 3.3 V power supply. The system includes an internal fully adjustable triangle-wave oscillator, which is used to generate the PWM carrier. Delivering an output power of 300 mW is a differential bridge (7.5 cm pMOS, 3 cm nMOS), driving a 16 Ω load. The THD+N of the system is less than 0.2%, and the efficiency at 300 mW is 89%.