A Wideband three-stage rail-to-rail power amplifier driving large capacitive load

This paper presents a wideband three-stage rail-to-rail power amplifier for driving large load. The proposed amplifier introduces two nulling resistors to the nested Miller compensation with feed-forward transconductance (NMCF) amplifier. The nulling resistors transform all zeros to left-half-plane (LHP), thereto optimize the phase margin of the amplifier. The strict matching problem of nulling resistors is alleviated in the proposed amplifier. The proposed compensation method is suitable to construct an amplifier with rail-to-rail input/output swing by using a complementary input differential pairs and class-AB output stage as demonstrated in the presented design example. Linearity is promoted by applying separate biasing voltages to the output stage. The proposed amplifier is fabricated with 0.35 mum 1P4M CMOS technology and the measurement results are presented, which verify the overall performance.