The STN1NF20 is a 200 V, 1 A N-channel power MOSFET from STMicroelectronics' STripFET™ II series, housed in a surface-mount SOT-223 package.
That is the conduction loss floor at 25 °C junction; multiply by the temperature coefficient from the datasheet's normalised curve to budget for the 150 °C hot case. Gate charge totals 5.7 nC at 10 V, which means a simple 10 V gate-drive rail with a 10 Ohm series resistor can switch this FET at 100 kHz without exceeding the driver's peak current capability.
Military temperature range — rated for harsh environments
The 2 W power dissipation at 25 °C ambient assumes a minimum copper area on the SOT-223 drain tab; derate above that temperature per the package's thermal resistance.