Design of a Class-D Audio Amplifier With Analog Volume Control for Mobile Applications

A class-D audio amplifier with analog volume control (AVC) for portable applications is proposed in this paper. The proposed class-D consist of two sections. First section is an analog volume control which consists of an integrator, an analog MUX and a programmable gain amplifier (PGA). The AVC is implemented with three analog inputs (Audio, Voice, FM). Second section is a driver which consists of a ramp generator, a comparator, a level shifter and a gate driver. The driver is designed to obtain a low distortion and a high efficiency. Designed with 0.18 um 1P6M CMOS technology, the class-D audio amplifier with AVC achieves a total root-mean-square (RMS) output power of 0.5W, a total harmonic distortion plus noise (THD+N) at the 8-Ω load less than 0.06% and a power efficiency of 90% with a total area of 1.74 mm2.