Then we can define the cut-off region or “OFF mode” when using an e-MOSFET as a switch as being, gate voltage, VGS < VTH and ID = 0. For a P-channel enhancement MOSFET, the Gate potential must be more positive with respect to the Source.
2. Saturation Region
In the saturation or linear region, the transistor will be biased so that the maximum amount of gate voltage is applied to the device which results in the channel resistance RDS(on being as small as possible with maximum drain current flowing through the MOSFET switch. Therefore for the enhancement type MOSFET the conductive channel is open and the device is switched “ON”.