NONLINEAR DISTORTION AND NOISE ANALYSIS OF GENERAL GM-C FILTERS

Abstract

Systems such as Gm-C filters are ideally designed to exhibit linear characteristics. However, their components – especially transconductors – are intrinsically nonlinear. Although there exist many approaches that aim at reducing nonlinear effects while dealing with practical design problems, nonlinear distortion cannot be canceled out completely. Thus, it is important to estimate a degradation of filter performance caused by nonlinearities. In this paper we propose a simple and general method to perform a transient analysis of any Gm-C filter structure based on a matrix description and macro-modeling of transconductors. An analytical description of general Gm-C filters with nonlinear transconductors is introduced. A differential system that determines dynamics of a general structure of Gm-C filter is formulated. This allows us to carry out an effective and fast transient analysis of any Gm-C filter using standard numerical methods. The approach can be applied to investigate any non-linear effects in filters. The noise analysis of Gm-C filters in general setting is also presented. The accuracy of the proposed methods is confirmed by comparison with SPICE simulation. Example of application for performance optimization of 4th order Chebyshev filter is given.