Class-AB high-swing CMOS power amplifier

A power amplifier for a loudspeaker and the earpiece of a telephone subset, integrated in the codec chip ARCOFI-SP (audio ringing codec filter featuring speakerphone function), are presented. The ARCOFI-SP is part of a subscriber telephone chip set. The analog section of the receive path comprises a low-noise programmable gain microphone amplifier with a maximum gain of 30-dB followed by a 16-b second-order sigma-delta analog-to-digital (A/D) converter. The analog section of the transmit path consists of two 16-b second-order sigma-delta D/A converters, one driving a pair of handset amplifiers for 200- Omega differential load and the other one a pair of loudspeaker amplifiers for 50- Omega differential load. The loudspeaker amplifier is described. A digital signal processor calculates the filter functions and handles frequency and tone generation. The amplifier has 1.2-mA quiescent current, 64-mA peak current, and >60 dB S/THD with 3.2-V output swing into a 25- Omega load.