Fully Differential, Bulk-Driven, Class AB, Sub-Threshold OTA With Enhanced Slew Rates and Gain

Abstract

This paper presents a single-stage ultra-low-power fully differential operational transconductance amplifier (FD-OTA) with rail-to-rail linear input range operating in weak inversion region. The input core of the OTA is comprised of source degenerated, flipped voltage follower (FVF)-based bulk-driven class AB input pair, into which a regenerative feedback loop has been inserted to boost its bulk transconductance ([Formula: see text]). The proposed FD-OTA has utilized self-cascode current mirror (SC-CM) loads, which increase its open loop gain from nominal intrinsic value of 42[Formula: see text]dB to 70.4[Formula: see text]dB. It has provided 9.24[Formula: see text]kHz gain bandwidth (GBW), consuming 64[Formula: see text]nW of quiescent power from a 0.51[Formula: see text]V single power supply at 15[Formula: see text]pF load. The proposed OTA in unity gain configuration has ensured reduced total harmonic distortion (THD) of [Formula: see text][Formula: see text]dB at 200[Formula: see text]Hz frequency and 1[Formula: see text]V[Formula: see text] signal swing. Its fully differential class AB input and output structures have ensured increased gain, GBW, slew rates and output swings with reduced nonlinearity and common mode substrate noise. The Cadence Virtuoso environment using GPDK 180[Formula: see text]nm standard [Formula: see text]-well CMOS process technology has been used to simulate the proposed circuit.