Do you want the curves to appear all together automatically?
Do you want to do this without spending money?
For automatic control, a Keithley 2601B would be connected to the gate. You would use TSP Express to set up the gate steps and drain sweep. Here is a video of the 2651A being controlled by TSP Express:
http://www.keithley.com/centralized_dis ... etid=55810
http://www.keithley.com/centralized_dis ... etid=57015
The demonstrations are for 2-terminal devices. To test your 3-terminal device, you configure TSP Express for a two SMU step and sweep family of curves. It is easy and quick to set up.
If you do not want to spend money, you would need to manually set the gate voltage and then run a TSP Express sweep to plot the curve.