⁶Many physical MOSFET models for circuit simulation still contain a number of undesirable modelling artefacts like unintended discontinuities or nonmonotonicities, which makes it difficult to decide whether it makes any sense to try to model their behaviour with monotonic and infinitely smooth neural models, developed for modelling smooth physical behaviour. Physical MOSFET models are often at best continuous up to and including the first partial derivatives w.r.t. voltage of the dc currents and the equivalent terminal charges. Quite often not even the first partial derivatives are continuous, due to the way in which transitions to different operating regions are handled, such as the drain-source interchange procedure commonly applied to evaluate the physical model only for positive drain-source voltages V _ds, while the physical model is unfortunately often not designed to be perfectly symmetric in drain and source potentials for V _ds approaching zero.