The STP4NB80 is an 800 V, 4 A N-channel PowerMESH MOSFET in a TO-220-3 through-hole package. Its 800 V drain-source voltage (Vdss) targets offline flyback converters, PFC stages, and auxiliary power supplies where the bulk rail sits at 400 V or higher. The 4 A continuous drain current is case-limited at 100 W dissipation — real-world current handling depends on heatsink and ambient, but the silicon is sized for several amps in a typical 100 W-class converter. On-resistance is 3.3 Ohm maximum at 2 A with 10 V gate drive. That is high by modern super-junction standards, so conduction losses dominate in continuous operation.
Obsolete — sourcing reality and what replaces it
Because no pin-compatible second source is documented, a cross-reference search should start with ST's own PowerMESH family at the same voltage and current class — the STP4NB80's 800 V / 4 A / TO-220 footprint is a common slot that several active ST parts may fill, but each candidate must be verified against the original design's gate drive and switching loss budget.
Package and thermal — TO-220 mounting notes
The STP4NB80 comes in a standard TO-220-3 through-hole package (supplier device package TO-220). The metal tab is the drain. Mounting requires a heatsink for any continuous current above an amp — the 100 W maximum dissipation is case-referenced, and without a heatsink the junction reaches 150 °C at a fraction of that power. Use a thermal pad or mica insulator with thermal compound, and torque the mounting screw to the usual TO-220 spec.