Optimized Active Single-Miller Capacitor Compensation With Inner Half-Feedforward Stage for Very High-Load Three-Stage OTAs

Optimized Active Single-Miller Capacitor Compensation With Inner Half-Feedforward Stage for Very High-Load Three-Stage OTAs

A new effective single-Miller capacitor compensation topology for three-stage amplifiers with very large capacitive loads, realized through an active-feedback capacitor together with an inner half-feedforward stage. More-over, an optimized design strategy which profitably exploits the two left half-plane zeros is presented. To improve the amplifier large signal transient response, the topology also includes an exter-nal feedforward path, that only marginally affects the frequency compensation, and a novel slew-rate enhancer section. To validate the solutions presented, a three-stage OTA driving a 10-nF load has been designed and implemented in a standard 0.35-?mCMOS technology. The amplifier occupies less than 0.003-mm 2 of die area, provides 2.7-MHz gain- and width product and 0.55-V/?s average slew-rate, while consuming only 25-?A quiescent current