A study of dc operating point shifts in MOSFETs with large RF signals

Abstract

AbstractUndesired behavior caused by radio frequency (RF) noise in an automotive integrated circuit (IC) is a serious problem to be solved in order to improve the reliability of automotive electronic systems. In this paper, we measured the VD–ID characteristic changes of a MOSFET (Metal‐Oxide‐Semiconductor Field Effect Transistor) when a large RF signal was injected into the gate or the drain at 100 MHz to 2 GHz. The following changes were observed when RF was injected at the gate: (1) the drain current increases in the saturation region, (2) the drain current varies in the linear region, and (3) negative drain current flows near VD = 0. We found that (1) and (2) were caused by nonlinearities of the VD–ID characteristic, and (3) was generated because the injected RF is voltage divided by the gate oxide film capacitance and the parasitic resistance of the bulk, and the forward current of the parasitic diode that was formed between the bulk and the drain flowed. In addition, a large negative drain current generated near VD = 0 when RF was injected into the drain. This was also produced to make the forward current flow in the parasitic diode between the bulk and the drain. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(7): 18–26, 2001