A workaround to the higher order derivative issue of threshold voltage based MOSFET models

Simulation of higher order nonlinear device currents in RF integrated circuits becomes crucial when high linearity is a design goal. Prediction of the nonlinear behavior of passive circuits like mixers, attenuators or switches play an important role in low-distortion designs, but also causes trouble due to the inability of threshold voltage based compact models to inherently model higher order nonlinearities around zero drain-source voltage. This paper introduces a systematic workaround enabling the designer to receive qualitative higher order simulation data around that important operating point when there is no access to one of the advanced surface potential or inversion charge based transistor models.