100 V, 30 A FERD — the conduction-loss trade-off
The ST FERD30H100STS is a 100 V, 30 A average-rated Field Effect Rectifier Diode in a TO-220AB through-hole package. ST's FERD (Field Effect Rectifier Diode) technology combines a merged PiN-Schottky structure to deliver a forward voltage of 745 mV at the full 30 A rating — lower than a conventional ultrafast recovery diode at this current, though the 130 µA reverse leakage at 100 V is higher than a standard Schottky's.
Forward drop vs leakage — where the FERD fits
At 30 A the 745 mV forward drop translates to roughly 22 W of conduction loss at full current — a number that drives the heatsink selection. The TO-220AB tab, when bolted to a proper heatsink with thermal compound, keeps the junction-to-case temperature rise manageable. The 130 µA leakage at 100 V adds negligible standby loss in continuous-conduction designs but becomes a factor in high-temperature idle conditions where the leakage doubles with every 10°C rise above 25°C. The Fast Recovery =< 500ns, > 200mA (Io) spec classifies this as a fast-recovery rectifier — not an ultrafast (< 50 ns) part, but fast enough for line-frequency and moderate-frequency switching in the 20-100 kHz range typical of PFC and flyback converters. Above 100 kHz the recovery losses start to dominate; a true ultrafast diode would be a better fit.
Package and mounting checklist
The TO-220-3 (TO-220AB) package has a standard 2.54 mm pin pitch and a metal tab with a 3.7 mm mounting hole for bolt-down heatsinking. The through-hole leads suit wave-solder assembly and manual rework. The tube shipping medium is typical for through-hole power devices — no reel, so pick-and-place requires tube feeders or manual insertion.
ST continues to manufacture the FERD family for the industrial and automotive power markets. The part is ROHS3 compliant, meeting the current EU exemption limits. For dual-sourcing resilience, a buyer would need to qualify a similar-rated 100 V, 30 A TO-220AB diode from another manufacturer — typically a Schottky or ultrafast recovery diode — against the specific switching frequency and thermal profile of the application.