MOSFET (3-terminal measurement)

[ainat]

Hi,

I am trying to do the MOSFET characterization with Keithley 2400 and Keithley 6487 using LabVIEW. The program will be such that Keithley 6487 will sweep the gate voltage and Keithley 2400 will sweep drain-source voltage and measure drain-source current for each Vgs.

The program I have done works well partially. This is because after certain voltage value of Vd-s, the curve droops down i.e the current decreases which shouldn't be the case. I am checked the speification sheet for the MOSFET as well. It works well when Vd-s is sweeped from 0V to 5V with Vg-s changing from 2V to 6V.

I am quite sure that the MOSFEt is fine. However, I am not sure why it shows a decreasing slope suddenly.I am unable to figure out the problem in my program

Please help.

I am attaching my program and also the result.

[apok]

just a thought....what is the current rating of the fet, also what is the part#

[jyang72211]

what about current/voltage limit setting for the instruments?

[ainat]

The FET part no is 2N7000.

The current rating is 1.05 Ampere for Keithley 2400.

I am attaching the actual plot for that MOSFET.

[apok]

your fet is not rated to drive more than 0.4amps?

[ainat]

If you see my graph which i got from the program, you will find that it goes to a value of 0.8 amps for Vgs=5V, but drops down when Vds crosses 3V. I am not sure why this beahvior? Is there any specific problem with my program?