matching FETs and found leaking?

[bigpanda]

I have purchase some IRFP240 and 9240 from a distributor. When I try to match the 9240 by applying a 15Vdc and a 150ohm resistor in series with the D,S, I found some of them give me a steady ready of about 3.6-3.8V (+ or - doesn't matter) which is normal, but some of them (about 20/50) cannot sustain a steady voltage. Does it mean that these are leaking badly and are no good? I wonder if the distributor would do anything about it.

Thanks for shedding a light.

 

[Pit Bull Ears]

Seems if the ones you suspect are leaky they should show some current when Vgs=0v. If it's gate to drain leakage, stiffining your gate drive should reduce the effect you are observing. Finally, if it's leakage it will be affected by temperature. As your IRFxxx warms up the leakage will increase.