High PSRR Class AB Power Amplifier

A simple class AB power amplifier topology for wide supply range is presented, which combines feedback type class AB biasing with low voltage gain boosting. The amplifier uses Miller compensation with nulling resistor, but avoids typical poor midband power supply noise attenuation of Miller compensated amplifiers by creating a cancelling signal path from the power supply to the output, using limited gain boosting amplifier bandwidth and bias network. The amplifier achieves 10.6MHz unity gain frequency with phase margin of 51deg when driving 20pFpar10kOmega load and has approximately 63dB positive power supply noise attenuation at 100kHz frequency, while drawing 298muA from 3V supply