This is a semi-empirical model derived from the Level 2 model. In the 80s this model has often been used for digital design and, over the years, has proved to be robust. A discontinuity in the model with respect to the KAPPA parameter has been detected (see [10]). The supplied fix has been implemented in Spice3f2 and later. Since this fix may affect parameter fitting, the option badmos3 may be set to use the old implementation (see the section on simulation variables and the .options line). Ngspice level 3 implementation takes into account length and width mask adjustments (xl and xw) and device width narrowing due to diffusion (wd).