Current-reuse single Miller feedforward compensation for multi-stage amplifiers

Presented is a novel current-reuse single Miller feedforward compensation (CRSMFC) scheme for multi-stage operational amplifiers (opamps). The proposed scheme introduces an implicit feedforward path into an opamp by reusing the current of the input stage, which creates a left-half-plane zero to cancel out the first non-dominant pole in the transfer function, thus improving phase margin and gain bandwidth product (GBW) without extra power consumption. A three-stage opamp prototype with proposed CRSMFC is realised in standard 0.18 μm CMOS process, and measured results show that it achieves a GBW of 4.4 MHz and a phase margin of 73° while driving a large capacitive load of 250 pF with only 34 μW of power consumption, implying a superior FoM over the state-of-the-art.