40 A, 400 V standard triac in TOP-3 insulated
The STMicroelectronics BTA41-400BRG is a standard triac rated for 40 A RMS on-state current and 400 V off-state voltage, housed in a TOP-3 insulated through-hole package. It handles non-repetitive surge currents of 400 A at 50 Hz and 420 A at 60 Hz, making it a fit for AC load switching in industrial motor drives, HVAC contactors, and power controllers where the insulated tab simplifies heatsink mounting without extra isolation hardware.
The 40 A RMS current rating sets the continuous load capability — size the heatsink and PCB traces for that level, and derate for ambient temperature above 25 °C. The 400 V off-state voltage suits 230 VAC and 277 VAC line switching with margin for mains transients. Gate trigger current is 50 mA max and gate trigger voltage 1.3 V max, so standard logic-level or microcontroller-driven optotriac circuits can fire it directly. Hold current of 80 mA max means the triac stays latched once triggered unless the load current drops below that threshold — check your minimum load if driving a small transformer or LED dimmer.
There is no official ST successor listed for this order code.
That saves assembly steps and reduces thermal resistance compared to a non-isolated package with a mica spacer.