MOSFET capacitance and conductance in the saturation regime

The relationship between capacitance and conductance of a MOSFET is examined in the region where velocity saturation dominates. In this domain it is shown that charge on the drain terminal (physically distinct from that in the channel) most be considered in order to keep the model from predicting the unphysical result that C_gd is negative. It is also shown that, under the same assumptions, g_m<C_gg/τ where g _m is the transconductance, τ is the transit time, and C_gg is the gate capacitance