25 A RMS, 800 V — sizing the triac for the load
The BTB24-800CWRG is an STMicroelectronics Snubberless™ Alternistor triac rated for 800 V off-state voltage and 25 A RMS on-state current. It handles the full-wave AC load in applications like motor speed controllers, industrial heaters, and professional lighting dimmers where the load current peaks well above the continuous rating. The non-repetitive surge current rating is 250 A at 50 Hz and 260 A at 60 Hz — this covers inrush from incandescent lamps or motor start-up without exceeding the device's SOA.
Snubberless™ — no RC network needed
The Alternistor construction with Snubberless™ technology means the triac can commutate inductive loads — fans, pumps, transformer-coupled loads — without an external snubber RC network. This saves two passives per phase and reduces PCB area. Gate trigger current is 35 mA max, gate trigger voltage 1.3 V max — compatible with standard optocoupler or microcontroller-driven gate drive circuits. The 50 mA max holding current ensures the device latches on through the zero-cross of a typical AC mains cycle.
ROHS3 compliant.
TO-220 package — thermal design
Through-hole TO-220-3 package with the tab as the thermal path. Heatsink selection depends on the RMS load current and ambient — the 25 A rating assumes a properly sized heatsink; at lower currents a clip-on or PCB-mount heatsink may suffice.