Consider first that the source and p-type substrate are grounded (at zero
potential) and the gate is “floating”; that is, the gate is not connected to an external
source of emf. Let a potential VDS be applied between the drain and the
source, such that the drain is positive. Electrons will then flow through the n
channel from source to drain, and the conventional current IDS, as shown in Fig.
41-20, will be from drain to source through the n channel.