The International Rectifier IRF640 is an N-channel power MOSFET built on the MESH OVERLAY™ technology. The TO-220-3 through-hole package bolts into a heatsink and is easy to swap in the field with a screwdriver and a bit of thermal compound.
The IRF640 is listed as obsolete. If you have this part on a BOM, you need to source it through the surplus or broker channel, or qualify a replacement.
Gate charge is 72 nC at 10 V, so the driver must supply that charge per switching cycle. Input capacitance is 1560 pF at 25 V drain — a modest load for most gate drivers.