A.1.2.3 Moderate Inversion

The transition between weak and strong inversion is called moderate inversion and extends over several thermal voltages. For many applications, especially, in ULP circuits operating at optimum speed or optimum $\ensuremath{E_{\mathit{s}}}\xspace \ensuremath{t_{\mathit{d}}}\xspace$ this region is critical, A simple closed-form drain-current equation is not available (with the only exception of the EKV model interpolation function [42, Chapter 7] (see also (4.5)) and even more sophisticated device models show poor accuracy in this operating region.