Measuring IV charachterstics at LN2 temperatures (Help!)

Is there a better way to do this - the right way?

Are you sure your resistor is resisting the low temps?

The temperature coeficient of the drain current for a fixed gate voltage varies with current and goes from positive at low current to negative at high current. at least thats what most of the datasheets show at more normal temperatures. this would sugest to me you are running the device at a low current.

Colin =^.^=

A possible source of problems could be the bonding.

Rene

The resistors i am using are metal film and are supposed to be fine upto 4 Kelvin. I am taking them only to 77 Kelvin, in my present experiments. The drain current goes upto 25 mA for some values of VGS. Rene, by bonding you mean the connections? The solder joints?

Almost. You're using a FET and this is a piece of semiconductor in a plastic case. The pins are connected to the semiconductor through bond wires, usually gold. This connection, between the semiconductor and gold, could break from thermal strain.

Rene

Thanks Rene for the reply. No, I don't think there is a bad connection as i can still turn off the FET by applying a higher negative gate voltage, -1.2 in my case. But you have a point the thermal strain due to unequal expansion may cause a bad connection. I have to keep that in mind.