Simple Analytical Modelling of an Electronically Tunable Potentiometer and Body Factor Influence

This paper presents a simple analytical modelling of a Electronically Tunable Potentiometer (ETP) circuit, made of a pseudo-resistor pair and a feedback mechanism that keeps resistance invariant to common mode voltage. The modelling utilizes the first order quadratic equations for the MOS transistor. In order to validate the analytical model, a Verilog-A model was written using the same MOS equations, and later matched to the ibm 130nm technology node resulting in a satisfactory approximation, with relative errors within 15%. Analysis of the ETP control voltage, pseudo-resistor current and pseudo-resistor resistance using the simple model were performed as a function of body factor. When the body factor decreases (better gate to channel electrostatic coupling) the pseudo-resistance increases for the same silicon chip area.