Design of CMOS Class AB Bridged Audio Amplifier: A Tutorial

Abstract

This article presents a tutorial on the design of CMOS Class AB bridged audio amplifier. High power efficiency is achieved by using a bridged output stage. An added advantage of the bridged amplifier is that the output stage can operate without the use of any capacitor, which supports the circuit to be operated under single rail power supply. An example of 3 ${\text{W}}_{RMS}$ audio amplifier with $3\Omega$ load is presented in this tutorial together with detail analytical analysis to demonstrate how to design a similar CMOS audio amplifier. The design example is simulated with a commercial 0.5 $\mu$m CMOS process together with measurement results from fabricated silicon to sustain the presented design methodology. The fabricated amplifiers can achieve low quiescent power at 33 mW, and a wide peak-to-peak output voltage swing of 8.5 Vpp subject to a 5 V supply. The THD of the amplifier is measured to be smaller than 10$\%$.