The application of a negative VGs, however, sets up an electric field that repels the charge carriers (electrons) from a portion of the channel beneath the silicon dioxide layer, causing the formation of a non-uniform depletion region, as shown in Figure 7-36(b). The width of the depletion region is directly proportional to the amount of the negative VGs applied at the gate-source terminals. The negative voltage VGs that causes the total depletion of the channel and stops the flow of the drain current completely is called the gate-to-source cut-off voltage V The voltage VGs is equal to the pinch-off voltage GS(off) VP in absolute value. That is:
Since the gate in depletion MOSFET is insulated from the channel, the gate-to-source voltage VGs can also be positive, in which case more charge carriers are attracted to the