250 V drain-source, 8 A continuous — a mid-voltage power switch
The STP8NS25: Packaged in a standard TO-220-3 through-hole case, it suits medium-voltage power switching in off-line supplies, DC-DC converters, and motor control circuits where a 250 V blocking voltage and single-digit amp current are the operating range.
Obsolete — planning a replacement now
STMicroelectronics lists the STP8NS25 as obsolete. For a new BOM line or a repair stock holding, you are looking at the surplus and broker channel. The TO-220-3 footprint is a common one, so a pin-compatible N-channel MOSFET in the same voltage and current class — 250 V, 8 A — from another manufacturer can be qualified as a drop-in. The gate charge of 51.8 nC at 10 V and input capacitance of 770 pF at 25 V are the numbers to match when screening a replacement, since they drive the gate-drive losses and switching speed.
Date-code and lot traceability are verified before shipment — the TO-220 body and laser marking are checked against known-good STMicroelectronics production runs to screen for re-marked or counterfeit material.