An Enhanced ACBC Three-Stage Amplifier using Complementary Indirect Miller Compensation

The design of operational amplifiers faces the tradeoff between power and speed. Increasing power-efficiency according to a certain speed requires a multi-stage design with an optimal compensation network that should be stable under all possible operating conditions. From this point of view, this paper proposes a three-stage operational amplifier with an enhanced AC boosting compensation (ACBC) using complementary indirect Miller compensation. The proposed amplifier is implemented in GlobalFoundries 22FDX (22 nm FD-SOI technology). In the worst case of the post-layout simulation, the proposed design provides a power efficiency IFOMs of 231k MHz·pF/mW, which is 2x larger compared to similar designs with ACBC as the standard compensation technique while driving a 500 pF load. According to this IFOMs, the design achieves an open-loop gain of 103.5 dB, a gain-bandwidth product of 8.5 MHz with a phase margin of 41.4 ° while the amplifier operates with a 10% reduced supply voltage of 0.72 V in ss-corner under 125 °C. A total current of only 18.7 µA, including the bias-network, is consumed.