Low Power Complementary Metal-Oxide Semiconductor Class-G Audio Amplifier With Gradual Power Supply Switching

The architecture, design and implementation of a low power complementary metal-oxide semiconductor (CMOS) class-G audio amplifier with gradual power-supply switching (GPSS) are presented. The proposed class-G amplifier output stage strategically uses the parallel connection of a class-AB output stage operating from smaller supplies (V-DDL/V-SSL), and a class-C output stage (with crossover from V-SSL to V-DDL) operating from higher supplies (V-DDH/V-SSH). GPSS is achieved using an efficient biasing scheme with level shifters. Moreover, the proposed biasing scheme in conjunction with negative feedback enables low distortion during the power-supply transition. Experimentally, the class-G amplifier prototype achieves a -82.5 dB THD + N, a peak load power of 50 mW and a quiescent power consumption of 350 mu W. The proposed class-G amplifier was implemented in a standard CMOS 90 nm technology and occupies an active silicon area of 0.08 mm(2).