A highly linear pseudo-differential transconductance [CMOS OTA]

This paper presents a pseudo differential, fully balanced, fully symmetric CMOS operational transconductance amplifier (OTA) with inherent common mode detection which shows a very linear behavior at frequencies around 10.7 MHz. A proposed feedback circuit helps to linearize the output while keeping the output voltage controllable. The OTA linearity behavior is measured in a unity voltage gain configuration which is the worst case for Gm-C filter realizations. Measurement results show an HD3 of -80 dB at 10.7 MHz with 1-Vp-p input signal. Two tone intermodulation measurement results show -70 dB from 1 MHz up to 10 MHz. The OTA is fabricated in the AMI 0.59 μm CMOS process and consumes 6 mA current drawn from a ±1.65 V power supply and occupies a small area of 118 μm×160 μm.