So pin 2 (the tab) of a FET in a D²PAK package will nearly always be the drain.

In a D²PAK (as well as many other common packages), the bottom of the die is attached directly to the leadframe's tab, since (among other reasons) this provides good thermal contact between the die and the package (and any heatsink the package is attached to). The reason you can't find any FETs with the pinout you want is a practical one: due to the way VDMOSFETs (a category that includes almost all currently produced discrete MOSFETs) work, the source and gate are on the top of the silicon wafer and the drain is on the bottom. You've learned an important lesson today, to always double check your package pinouts!įor the purposes of running tests, you may be able to just cut the traces on the PCB and use wires to connect the FET to what it should be connected to, or connect it with wires while it's insulated from the board, but doing either of these in production is a bad idea. The IRF640 is an N Channel enhancement mode power MOSFET designed, tested, and guaranteed to withstand a specified level of energy in the breakdown avalanche mode of operation. It's unfortunate, but you probably just need to get new PCBs made.

Free download mosfet pinout