Gate Bias Dependence of Substrate Signal Coupling Effect in RF MOSFETs

Abstract

Analytical expressions for the Y-parameters of RF MOSFETs including the substrate signal coupling effect were systematically derived. The expressions are physically correct and simple enough to be intuitive. With the expressions, how signal coupling occurs through the substrate network of parasitics could be clearly explained in physical terms, for the first time. In particular, we focused on how substrate signal coupling makes an influence on the output admittance of an RF MOSFET as the gate bias varies. The developed theory was verified with S-parameter measurement results.