200V, 18A N-channel — the switching envelope
The STP20NF20: Gate charge totals 39 nC at 10V, and input capacitance is 940 pF at 25V drain bias. These numbers drive the gate-driver sizing: a 1A gate-driver can switch the gate in roughly 39 ns, though layout parasitics and the Miller plateau extend the real transition time. The ±20V Vgs(max) gives margin for gate overshoot in hard-switched bridges.
Thermal and mechanical fit
The TO-220-3 through-hole package mounts into a standard 0.100-inch pitch footprint with the tab as the drain connection. Maximum power dissipation is 110W at case temperature — derate this when the case runs above 25°C. Gate threshold is specified at 4V maximum with 250µA drain current, so a 5V logic-level gate drive may not fully enhance it — the datasheet's 10V drive voltage for the rated Rds(on) means a 12V or 15V gate rail is the safe choice for minimum on-resistance.