A High-Performance Fast Switching Charge Dump Assisted Class-K* Audio Amplifier

Abstract

A new Class-K* audio amplifier with high-power efficiency and high fidelity is integrated in a 0.35-mu m CMOS process. It proposes a new topology connected Class-D amplifier with fast-switching charge-dump (FSCD) amplifier in parallel. The integration of the amplifier requires neither analog buffer amplifier nor a complex compensation circuit needed in hybrid audio amplifier (Class-K). The FSCD amplifier composed of comparators and switches works at a high-switching frequency in order to absorb the distortion caused by Class-D amplifier switching. Thus, this assists the audio amplifier to have good linearity under switching operation. With the proposed topology, the audio amplifier has a flat frequency response with -3-dB bandwidth of 60 KHz and is capable of delivering up to 257 mW into 4.1-Omega load with maximum efficiency of 81%. A typical total harmonic distortion plus noise (THD + N) is less than 0.1% at the power level over 25 mW within the audio frequency range (20 Hz-20 kHz), and the minimum THD + N is 0.025% with the audio input frequency of 1 kHz at the output power of 114 mW.