A novel feed-forward compensation technique for single-stage fully-differential CMOS folded cascode rail-to-rail amplifier

Abstract

This paper presents a novel active and passive mixed feed-forward compensation technique for single-stage CMOS folded-cascode rail-to-rail operational trans-conductance amplifiers (OTA). Simulations using 0.5 μm Agilent CMOS process parameters indicate a phase margin of around 82° with an unity gain bandwidth of 320 MHz (@1.17 pF capacitive load including the device parasitics). Also, the compensated OTA provided over 60 dB DC-gain with rail-to-rail output voltage swing as well as wide input common-mode range. This ensures optimum step response (fast and accurate settling without ringing) for the feedback amplifier in switched-capacitor signal processing applications. An improved ``fast sensing'' common-mode feedback circuit with high common-mode gain is also used for the single-stage cascode OTA.