An approximate analysis and its application to the nonlinear performance of three MOSFET transconductance amplifiers

Muhammad Taher Abuelma'Atti

doi:10.1016/0026-2692(95)00013-8

Abstract

A simple procedure for approximating the input-output characteristic of nonlinear electronic circuits is presented. Using this procedure, closed-form analytical expressions, in terms of the ordinary Bessel functions, are obtained for the output spectra of a nonlinear electronic circuit resulting from a multisinusoidal input. Using these expressions, the nonlinear performance of three basic MOSFET transconductance amplifiers is considered in an attempt to determine the transistor parameters for best linearity.

Highlights

It is frequently valuable in the design of analog signal processing circuits and systems to have an indication of the likely spectrum of output signals, including harmonics and intermodulation products, from a non-linear component of the system whose characteristics are known only in the form of an untractable mathematical expression relating its input and output variables
An alternative procedure, which permits the derivation of high-order product magnitudes from a simple model must, meet the following two principle requirements: a. the mathematical description, which is valid over a wide range of the input variable, must be of a kind that incorporates the major features of the characteristics of the non-linear component while still offering straightforward means for calculating harmonic and intermodulation products magnitudes; and b
The harmonic performance of three widely used MOSFET transconductance amplifiers will be considered as illustrative examples for the use of the procedure presented in the previous sections

Summary

INTRODUCTION

It is frequently valuable in the design of analog signal processing circuits and systems to have an indication of the likely spectrum of output signals, including harmonics and intermodulation products, from a non-linear component of the system whose characteristics are known only in the form of an untractable mathematical expression relating its input and output variables. A widely used procedure for evaluating output spectra involves derivation of a high-order polynomial approximation to the available untractable mathematical expression and this, in turn, implies the use of sophisticated curve-fitting techniques that invariably demand extensive computing facilities and well developed software. The mathematical description, which is valid over a wide range of the input variable, must be of a kind that incorporates the major features of the characteristics of the non-linear component while still offering straightforward means for calculating harmonic and intermodulation products magnitudes; and b. M.T. ABUELMA’ATTI having obtained such a mathematical model it must be possible to derive its parameters without recourse to the use of sophisticated curve-fitting techniques. ABUELMA’ATTI having obtained such a mathematical model it must be possible to derive its parameters without recourse to the use of sophisticated curve-fitting techniques It is the major intention of this paper to present such a procedure. Evaluation of the harmonic distortion performance of these amplifiers will be considered in an attempt to determine the transistor parameters for best linearity

PROPOSED APPROXIMATION

HARMONIC AND INTERMODULATION ANALYSIS

EXAMPLES

Example 2

Example 3

CONCLUSION