Mobility-reduction-free low-distortion OTA using backgate-bias technique

Abstract

This paper proposes a low-distortion CMOS operational transconductance amplifier (OTA) based on backgate-bias technique especially for an OTA using four MOSFET's operating in the non-saturation region as a voltage controlled current source (VCCS). In the VCCS two input signals are applied to two drain terminals of the four MOSFET's respectively and their gate-to-source voltages are kept constant. Therefore the VCCS is free from mobility reduction. To make backgate-to-source voltages of two MOSFET's in the VCCS equal to DC shift of input signals will reduce output current distortion of the OTA drastically. In addition to these features the proposed OTA is free from body effect even when it is realized by a single well process. Simulation results confirm the theory and the effectiveness of the proposed method.