Hi
How can I use MOSFET as a current source or variable load for voltage regulator. The plateau region of mosfet doesnot change the current on increasing the voltage. So how can I use MOSFET for linear change? Do I have to use feedback? How ? Thanks in advance!!

 

For a linear current load versus voltage you need to add an op amp such as the circuit here. The transistor is an N-MOSFET with whatever current capability you need. A logic level MOSFET would work best if you want to minimize the voltage supply required.

Remember that the transistor will be dissipating load power so will need to be on an appropriate heat sink.

The op amp can be a single supply device such as the LM324 so you would need only one supply voltage.