The STF7N105K5: The 1050 V Vdss rating suits offline flyback converters, PFC stages, and auxiliary power supplies running from rectified mains. The TO-220FP full-pack package isolates the tab from the heatsink, simplifying assembly in metal enclosures. That 2 Ohm figure at 10 Vgs is the number to use for conduction loss calculations in a hard-switched converter.
Gate-drive voltage and threshold — a checklist for the first prototype
The STF7N105K5 specifies a 10 V gate drive for the rated on-resistance, with a maximum gate-source voltage of ±30 V. The gate threshold voltage is 5 V maximum at 100 µA drain current. Input capacitance is 380 pF at 100 V Vds. Through-hole mounting in the TO-220-3 Full Pack package means the leads are designed for soldering into a PCB or wiring into a terminal block. The full-pack construction isolates the mounting hole from the drain, so no mica washer or sil-pad is needed when bolting to a chassis or heatsink — just thermal grease. That saves a BOM line and a manual assembly step.
The base product number STF7 covers the family, and the K5 suffix denotes the 1050 V variant.