Low power high bandwidth amplifier with RC Miller and gain enhanced feedforward compensation

An improved frequency compensation technique is presented for low-power low-voltage three-stage operational amplifiers with high capacitive loads. The technique uses single RC Miller compensation and a direct gain enhanced feedforward path from the input to the output. With a load capacitance of 300 pF, the amplifier nominally achieves a dc gain of 74 dB, a 3-dB bandwidth of 2.9 kHz, a 52 degrees phase margin, and a slew rate of 0.22 V/μs, while consuming 0.24 mW of power with a 1.2-V supply voltage, in a 180 nm CMOS technology. The 3-dB bandwidth is one of the highest reported for a high-gain three-stage CMOS amplifier.