Classification and Design Space Exploration of Low-Power Three-Stage Operational Transconductance Amplifier Architectures for Wide Load Ranges

Abstract

Since operational transconductance amplifiers (OTAs) form the basic building blocks of many analog systems, the compensation of three-stage OTAs has attracted a lot of attention in the literature. Many different solutions to the stability problem of such OTAs have been proposed over the past 20 years, with each solution exhibiting different properties or targeting a different application. This work surveys a broad selection of previously reported architectures and proposes a novel classification scheme that exposes features common to seemingly different compensation architectures and serves as a guideline for which type of OTA is suitable for a given application. In addition, a novel figure of merit (FoM) is proposed to guide the designer in deciding which OTA architecture suits the tradeoffs specific to the application at hand. Theoretical discussions are further reinforced by transistor-level simulation results.