0.7-V Bulk-Driven Three-Stage Class-AB OTA

A high-performance architecture for bulk-driven operational transconductance amplifiers (OTAs) is presented. The solution exploits a three-gain-stage topology and, as a distinctive behavior, provides an inherent class-AB performance with simple and robust standby current control. A 0.7-V supply OTA is designed using a 180-nm standard CMOS technology. Post layout simulations show a 61-dB open loop gain and a unity gain bandwidth of 3.6 MHz, under a capacitive load of 20 pF. Significant performance improvement when compared to prior art is achieved, so that the best figure of merit is found.