CMOS device modeling for subthreshold circuits

Simple models of MOS device behavior that covers the subthreshold regime and the transition to above threshold are explored. A formulation that appears to provide results as good as process variation permits and that is well-suited to efficient computation is proposed. 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 κ