Analysis of Stability in Multistage Feedforward Operational Transconductance Amplifiers using Successive One-Pole Approximation

TL;DR

This paper introduces a successive one-pole approximation method for analyzing the stability of multistage feedforward OTAs, enabling intuitive design and stability assessment for high-gain wideband applications.

Contribution

It develops a novel SOPA-based analysis technique for multistage feedforward OTAs, extending stability analysis from two to four stages.

Findings

SOPA effectively predicts stability margins.

Design guidelines for stable multistage OTAs are provided.

Analysis covers up to four-stage configurations.

Abstract

This paper presents analysis results of the operational transconductance amplifiers (OTAs) that combine feedforward paths and multistage amplifiers to achieve high-gain wideband operation as well as frequency compensation. To analyze multistage feedforward OTAs and provide an intuitive design method, the successive one-pole approximation (SOPA) is used for each substage of a multistage feedforward OTA. Using SOPA, the stability analysis is carried out from the two-stage feedforward OTA to the four-stage feedforward OTA in this work.