Time-Domain Analysis and Modeling of Large-Signal RFI Rectification in MOS Transistors

Based on theoretical and experimental time-domain results, this article analyses large-signal radio-frequency interference (RFI) rectification effects in small-signal low-frequency MOS transistors. Measurements indeed show that beyond the maximum operating frequency, transistors seem to exhibit RFI rectification, which is confirmed, with excellent agreement, by SPICE simulations. Transistors models used in these simulations are extracted from measurements, and include all the parasitic elements (package and circuit). After investigating transistors' internal currents, it appears that this rectification effect is not related to active nonlinearities of the device, but to the nonlinear capacitances of the transistors: the gate-drain overlap capacitance and, for the major part, to the parasitic drain-bulk junction capacitance. A simplified model reproducing this effect is presented, and the frequency range of occurrence of the RFI rectification is analyzed.