The BTA24-800BWRG is a Snubberless™ alternistor triac from STMicroelectronics, rated for 25 A RMS on-state current and 800 V off-state blocking voltage in a TO-220 through-hole package. The 25 A RMS rating is the continuous current the device can handle when properly heatsunk — for a resistive load like a heater bank or incandescent lamp string, that is the design ceiling.
Gate drive and trigger thresholds
The gate trigger current (Igt) is 50 mA maximum, and the gate trigger voltage (Vgt) is 1.3 V maximum. That is a standard drive level — a simple transistor or optocoupler driver with a current-limiting resistor can fire it. The hold current (Ih) is 75 mA maximum, meaning the load must draw at least 75 mA to keep the triac latched on after the gate pulse is removed; below that threshold the device will commutate off at the next zero-crossing. For low-current loads like a small fan or relay coil, verify the load current exceeds the hold current or the triac will drop out mid-cycle.
Surge capability and thermal margin
The non-repetitive surge current (Itsm) is 250 A at 50 Hz and 260 A at 60 Hz — that is the peak single-cycle pulse the die can survive for fuse coordination or inrush from a cold filament.