A nonlinear CAD model for the depletion-mode IGFET

Using simple charge-voltage relationships, a four terminal model is developed for the depletion-mode IGFET. Various conditions, which can co-exist at the surface such as accumulation, depletion and inversion, are taken into account. The basic model elements, namely the source-drain transport current and the various charging currents, are explicitly given in terms of known processing data. Device parameters essential to device design such as threshold voltage, drain saturation voltage and conditions for surface inversion are directly related to implanted layer characteristics.