800 V, 3 A — the power switch for off-line and high-voltage rails
The STD4NK80Z-1 is an N-channel MOSFET from ST's SuperMESH series, built for primary-side switching in off-line power supplies, LED drivers, and auxiliary converters where the DC bus sits at 400 V or higher. The 800 V drain-source rating gives you a solid voltage margin above a rectified 230 VAC rail, and the 3 A continuous drain current handles moderate power stages without oversizing the package. The gate charge of 22.5 nC at 10 V keeps switching losses manageable for flyback and forward converters.
Through-hole TO-251 — rework-friendly, but watch the tab
The TO-251 (IPAK) package is a three-lead through-hole with short leads and a metal drain tab that needs a good thermal connection to the board copper. The ±30 V maximum gate-source voltage means the gate driver should never exceed a 10 V drive for minimum Rds(on).
Temperature range and ruggedness for industrial environments
The SuperMESH structure gives good avalanche energy capability.
The base product number is STD4NK80, and the -1 suffix indicates the TO-251 package variant — the same die is also available in DPAK (STD4NK80Z) if a surface-mount option is preferred.