Charles daEngineer

n Stage Transconductance Amp

Published on Sat Nov 01 2025

Introduction

This article will become helpful in corrective feedback amplifier circuits for determining the minimum number of stages required to meet a desired bandwidth.

This is an n-stage amplifier

The strategy here is notice that $V_{2}$ is a function of $V_{1}$ :

$s C_{i s s} V_{2} = - g m V_{1}$

$∴ V_{2} = \frac{- g m}{s C_{i s s}} V_{1}$

now notice the voltage $V_{3}$ is also a function of $V_{1}$ :

$s C_{i s s} V_{3} = - g m V_{2}$

$s C_{i s s} V_{3} = - g m \frac{- g m}{s C_{i s s}} V_{1}$

$∴ V_{3} = {(\frac{- g m}{s C_{i s s}})}^{2} V_{1}$

I can perform a similar operation for each of the $n - 1$ stages to get the equivalent single stage transconductance amplifier:

This is a single stage amplifier which is equivalent to an n-stage amplifier