A High-Performance OTA with Hybrid of Inverter-Based OTA and Nauta OTA for High Speed Applications

Abstract

Operational transconductance amplifiers (OTAs) are widely employed as active elements in filters, data converters, and buffer amplifiers. Inverter-based implementation of OTAs is an attractive approach for low voltage realization of analog subsystems. However, there are still fundamental challenges such as how to simultaneously achieve high DC gain, bandwidth, speed, and good noise performance based on existing inverter-based OTA architectures. In this paper, a new two stage OTA, hybrid with current reuse inverter OTA and Nauta transconductor is proposed to improving performance by taking advantages of their own merits. The introduced architecture is keeping the merits of Nauta transconductor such as high bandwidth, high speed and the superior input referred noise performance of the current reuse inverter-based OTA. Furthermore, in order to reduce the PVT variations, bulk tuning circuits based on "detecting-feedback" loop applied on CMFB and the output stage of Nauta transconductor is proposed to dynamically tune the output DC levels under PVT variations. The proposed new hybrid OTA is implemented in 180nm CMOS technology and achieves very competitive performance compares with all inverter based OTAs and the other state-of-the-art OTAs.