I just want to characterize a Power P-MOSFET, Vth between -2 to -4 V with 100V allowed across channel. I want to use a function generator to pulse the gate. I also have access to oscillsocopes. I want to be able to measure VGS, VDS, and IDS.

Any thoughts?

 

Get the data sheet for the device. It usually shows the test setup the manufacturer used to characterize the FET.

 

Thanks. I will try using those circuits today. From looking at the data sheet, my circuit did not have a resistor on the gate.

 

That can cause problems. You can see the effect of the gate resistor on Ton and Toff as you vary its value.

 

Manufacturers do not use gate resistors for VGS, VDS and IDS measurements. These measurements are typically carried out with curve tracers. If you are doing it manually, make sure the function generator is capable of supplying enough current to quickly charge the gate capacitance within the specified measurement pulse width (usually 300us). You would also need a good power supply, which has a good step response to maintain constant VDS against pulsing IDS (also 300us).

How do you plan to read the results? Digital scope? Is it accurate enough? You need to read them within the 300us pulse width after the they stabilise. Using DC measurements are out of question due to the thermal changes which would affect the measurements.