1050 V N-channel MOSFET — primary-side switching for offline supplies
Its 1050 V drain-source breakdown voltage targets offline flyback converters, PFC boost stages, and auxiliary power supplies where 800 V rated parts leave insufficient avalanche margin. The 1.4 A continuous drain current and 60 W power dissipation suit low-to-moderate power stages, typically in chargers, adapters, and industrial bias supplies.
11 Ohm Rds(on) — conduction loss at low current
For a 1.4 A rated device this is a moderate figure; conduction loss at full current reaches about 22 W, which combined with switching loss pushes the junction temperature toward the 150°C maximum. The 13 nC gate charge keeps drive losses low, so the part works well with a simple gate-drive transformer or a low-current driver IC at switching frequencies up to 100 kHz.
STMicroelectronics lists the STP1N105K3 as Obsolete. Engineers evaluating a replacement should look for a 1050 V N-channel MOSFET in TO-220-3 with similar gate charge and Rds(on) — several manufacturers offer pin-compatible alternatives in the same voltage class.
TO-220-3 — through-hole for legacy board retrofit
The 150°C maximum junction temperature and 60 W power dissipation assume adequate heatsinking — a clip-on or screw-mounted heatsink is expected for continuous operation above 0.5 A. The package suits retrofit into existing boards where a surface-mount MOSFET would require layout changes.