Simple variable current source for approx. 2A, constant load
Something like this should work for you. With the values shown, R3 needs to be rated for about 1W and M1 needs a heat sink for up to 30W if RL can be shorted. The current sink has a compliance of the supply voltage minus about 0.5V so don't use excessive voltage for V1 (needs to be about 7V minimum for U1 to work properly) if you want to keep the heat sink reasonable. Or you can add a resistor in series with RL to move some of the power dissipation off the transistor.

"Or you can add a resistor in series with RL to move some of the power dissipation off the transistor." You mean from the Drain to GND, Right? 







simulate this circuit &ndash; Schematic created using CircuitLab