25 A RMS, 800 V — the load-switching anchor
The STMicroelectronics BTB24-800BWRG is a Snubberless™ Alternistor triac rated for 25 A RMS on-state current and 800 V off-state voltage, housed in a TO-220 through-hole package. The Snubberless construction means it commutates inductive loads — motors, solenoids, transformers — without the external RC snubber network that standard triacs need, saving board space and two passives per phase. The 800 V blocking voltage gives comfortable margin on 230 VAC and 277 VAC mains lines, even with the transients common in industrial and appliance environments.
Maximum gate trigger current (Igt) is 50 mA, and maximum gate trigger voltage (Vgt) is 1.3 V. That is a standard logic-level or microcontroller-port drive with a series resistor — no special gate-drive IC needed for most designs. The 75 mA maximum holding current (Ih) means the triac will stay latched once triggered as long as the load current stays above that threshold; below it the device turns off at the next zero-crossing. For low-current loads like small fans or indicator lamps, check that the load current exceeds Ih to avoid intermittent dropout.
Surge capability and junction temperature range
Non-repetitive surge current (Itsm) is rated at 250 A at 50 Hz and 260 A at 60 Hz — enough to survive the inrush from incandescent lamps, motor start, or capacitor charging without external soft-start circuitry in many cases. The TO-220 tab carries the heat; a heatsink is expected for continuous loads near the 25 A RMS rating.
It is a current-production ST part, so new designs and ongoing production can commit to it without obsolescence risk.