CMOS DEVICE MODELING FOR SUBTHRESHOLD CIRCUITS

There is a need for a simple model of MOS device behavior that covers the subthreshold regime and the transition to above threshold. The need for such a model will increase as increasing use is made of subthreshold operation for analog computation and for very low-power applications. This paper explores such models and proposes a formulation that appears to provide results as good as process variation permits, and which is well-suited to efficient computation. The exponential dependence of source-drain current on gate voltage in subthreshold implies that current values may be very sensitive to variation in parameter values (particularly those that appear in exponents). This problem is investigated, particularly with respect to threshold voltage, I0 and kappa.