A capacitor-free feed-forward compensated single-stage merged topology fully-differential CMOS folded cascode amplifier

Abstract

This paper presents a capacitor-free feed-forward compensation technique for single-stage CMOS folded-cascode operational transconductance amplifiers (OTA) using a "merged CMOS cascode transconductors" topology. A phase margin of around 65 degrees can be achieved without the use of any "added" load capacitance for the open-loop amplifier. This ensures optimum step response (fast 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.