900 V N-channel MOSFET for high-voltage SMPS
The STP8N90K5: The 130 W dissipation at the case tells you this part needs a heatsink — the TO-220 tab bolts to a thermal pad or chassis, and the junction-to-case thermal path is the limiting factor for continuous output.
130 W dissipation — heatsink is mandatory
The 130 W maximum dissipation at case temperature Tc is a junction-limited rating, not a free-air number. For the full 130 W, bolt the tab to a heatsink with thermal grease or a pad — the tab is the drain, so the heatsink may be at bus voltage unless you use an insulating washer. Gate drive threshold is 5 V maximum at 100 µA drain current, with the recommended drive voltage at 10 V for minimum on-resistance. The ±30 V gate-source maximum gives headroom for gate-drive transients in a hard-switching converter, but the 10 V drive rail is the practical target for a clean turn-on.
The 150 °C absolute maximum junction is the hard ceiling — the datasheet's safe-operating-area curves and thermal impedance numbers define how close you can run at elevated ambient.
The base product number STP8N90 covers the family; the K5 suffix identifies the MDmesh K5 generation, which is the current silicon.