In this paper we present an analytical model for charge injection in MOS switches that is valid for all regions of operation. The model is general and can be applied for different load conditions. We analyze and develop two separate charge injection models for the different operating conditions. A simple continuos model that is valid for all conditions is then stitched together using appropriate functions. Simulation results from this model agrees well with previously published measurement results. The model is used to predict charge injection error and nonlinearity. 1. INTRODUCTION Sample-and-holds (SH) are important circuit components in most modern analog sample-data systems. In general, in many such systems the overall system accuracy is limited by the nonlinearity introduced by the input sample-and-hold circuit. One of the limiting mechanisms for fully differential circuits is the nonlinearity introduced by the SH charge injection error [1]. Therefore, adequate modeling of charge...