Conductances
The concept comes from the small signal model of a transistor.
In the small-signal model, the change in the transistor current due to very small changes in each of the terminal voltages, can be expressed as conductances (gate, source and drain).
Referenced to the bulk voltage
Gate transconductance:
(how the current changes with a small change in the gate)Source conductance:
(how the current changes with a small change in the source)Drain conductance:
Referenced to the source:
By differentiating the equations with respect to the terminal's voltage, we obtain the "real" equations.
