1200 V drain-source — the voltage headroom that defines the application
The STW8N120K5: The 1200 V drain-source rating suits offline flyback converters, PFC boost stages, and auxiliary power supplies.
2 Ohm Rds(on) — conduction loss at the operating point
At 6 A continuous drain, the conduction loss at 2 Ohm is within the 130 W power dissipation limit at the case.
13.7 nC gate charge — switching speed without a heavy driver
Input capacitance Ciss is 505 pF at 100 V drain-source.
The 150°C maximum junction allows a higher case temperature in a sealed enclosure, but the 130 W power dissipation limit at the case must be derated above 25 °C per the datasheet curve.