A submicron DC MOSFET model for simulation of analog circuits

This paper presents an efficient dc MOSFET model for accurate simulation of analog circuits. A new approach to model channel length modulation is presented. An empirical expression for channel length modulation is derived from measurements. This is used to model the observed behavior of g_D with gate, drain, and substrate bias. Some of the models commonly used for circuit simulation do not predict the effects of gate and substrate bias adequately. A new smoothing function is used to unify the linear and saturation regions in a single expression. Continuity of transconductance is maintained between the weak and strong inversion regions. Model efficiency is maintained by avoiding the use of transcendental functions in the smoothing techniques. We demonstrate <2.5% rms error in predicting I_D, g_D, and g_m for a discrete device size and <4% rms error for models scalable over a wide range of width and length. Furthermore, we have experimentally characterized a CMOS inverter as well as an op-amp to show that our model improves prediction of circuit parameters. Errors in predicting the peak gains are reduced by at least half compared to earlier models