600 V blocking, 8 A continuous — the AC switching workhorse
The STMicroelectronics T835H-8T is a Snubberless™ alternistor triac rated for 600 V off-state voltage and 8 A RMS on-state current — a common choice for 230 V AC line switching in industrial and appliance loads where you need margin against mains transients. The Snubberless™ construction means the triac can commutate inductive loads without an external RC snubber across the main terminals, which saves two passives and a chunk of board area. The alternistor structure handles the dV/dt stress of motor and transformer switching better than a standard triac.
150°C junction — keeps the gate drive honest in a hot box
The 150°C Tj ceiling gives thermal headroom when the heatsink is undersized or airflow is blocked. Gate trigger current is 35 mA max and gate trigger voltage is 1 V max — both low enough to be driven directly by a microcontroller I/O pin through a series resistor, no extra driver transistor needed. The 35 mA holding current ensures the triac stays latched through the zero-crossing of a lightly loaded line.
Surge rating and package — what the repair bench sees
Non-repetitive surge current is 80 A at 50 Hz and 84 A at 60 Hz — that is the peak the die can survive for one cycle during a fuse blow or a capacitor inrush. The TO-220-3 through-hole package is the standard power tab; the metal tab is the MT2 terminal and needs either a heatsink or a soldered copper pour on the PCB to pull heat out.