An Improved Four-Port Equivalent Circuit Model of RF MOSFETs for Breakdown Operation

In this paper, an improved four-port radio-frequency (RF) model for metal-oxide-semiconductor field-effect transistors is extended to investigate the various RF breakdown phenomena where reliability is a concern for the first time. Reduction of isolation from drain to source as well as inductive behavior occurred at the drain, and source terminals in the breakdown region are analyzed and explained by using this modified four-port RF model incorporating with an inductive breakdown network. In addition, reduction of inductive source impedance in the breakdown regime is analyzed based on a series feedback mechanism and degradation of transconductance. Parameters of the modified four-port breakdown model are extracted by fitting measured four-port measurement data in the breakdown regime. Good agreement between measured and simulated 16 four-port scattering parameters (S-parameters) is achieved in the breakdown and saturation regions, validating the improved four-port breakdown model. Therefore, this model can be beneficial to RF amplifier designs in the breakdown regime with reliability considered.