Drain characteristics of an n-channel MOSFET is shown in figure below.
VGS can be positive and negative.The characteristics for p-channel are similar to the above figure excepts signs of current and voltage are reversed.
The transconductance curve(transfer characteristics)of depletion type MOSFET is shown in figure below.
This characteristcs shows the variation of ID with VGS.IDSS denoteS the drain current with shorted gate.The curve extends on both sides ie VGS can be negative as well as positive.Since VGS can be positive also IDSS is not maximum value of drain current.
This device has three regions.The ohmic region,active region and breakdown region.The rising position of the drain characteristics is the ohmic region.The device acts as resistor.The drain current is nearly constant in the active region.When VDS exceeds the rated value,avalanche breakdown occurs.This device has two applications ie as a resistor or a current source.
Mosfet can be used to make amplifiers – an example of a 18watt Mosfet amplifier is given here.