0.35-V SR-Enhanced Bulk-Driven OTA for Loads up to 10 nF

Abstract

This study presents a low-voltage bulk-driven CMOS operational transconductance amplifier (OTA) operating in the subthreshold region designed to drive loads up to 10 nF, which is the largest value for this class of amplifiers. To meet this goal, the solution exploits the body terminal of various active devices leveraging local positive feedback to enhance the input transconductance gain and implementing dynamic threshold voltage control in the output transistors. This, along with a Slew Rate Enhancer section, significantly improves the OTA current driving capability. Experimental measurements conducted on a prototype, implemented in a 60-nm technology and supplied from 0.35 V, confirm the expected performance demonstrating a SR of 1.1 V/ms for a 10-nF load with a limited quiescent current consumption of 1.4 μ A.