Last month I bought a couple of IRF5305 (click for datasheet) on Ebay. Today I soldered a couple of them in my PCB and had some issues with them. My FET schematic looks like the following:
According to the datasheet the gate-source threshold voltage lies somewhere between 2V and 4V. Now when I put logic '1' on the gate the gate-source voltage is around 1.7V. In this situation I would expect that the MOSFET will not conduct. However, in practice it did conduct and I could even power a small blue LED as load.
Now I played a little bit with the voltage on the gate, and it seems to be turned off once I put around 3.8V on the gate. So right now I'm guessing that either I'm doing something wrong, or that these 'chinese' MOSFETS are out of spec. I hope someone can help me out here.