A 0.6 V Bulk-Driven Class-AB Two-Stage OTA with Non-Tailed Differential Pair

Abstract

This work presents a two-stage operational transconductance amplifier suitable for sub-1 V operation. This characteristic is achieved thanks to the adoption of a bulk-driven non-tailed differential pair. Local positive feedback is exploited to boost the equivalent transconductance of the first stage and the quasi-floating gate approach enables the class AB operation of the second stage. Implemented in a standard 180 nm CMOS technology and supplied at 0.6 V, the amplifier exhibits a 350 kHz gain bandwidth product and a phase margin of 69° while driving a 150 pF load. Compared to other solutions in the literature, the proposed one exhibits a considerable performance improvement, especially for large signal operation.