1.2 kV off-state — where this SCR fits
The STMicroelectronics TYN1212RG is a standard-recovery SCR rated for 1.2 kV off-state voltage and 12 A RMS on-state current, housed in a TO-220AB through-hole package. This voltage class puts it squarely in 240 VAC line applications with healthy margin — the 1.2 kV Vdrm covers rectified mains up to 400 VDC bus rails and handles the voltage spikes common in motor-start and power-supply circuits without derating anxiety.
Current handling and surge capability
At 12 A RMS continuous, the TYN1212RG handles load currents typical of medium-power phase-control circuits — heater elements, small motor drives, and battery-charger front ends. The non-repetitive surge rating of 120 A at 50 Hz tells you the die can absorb the inrush from a capacitive input filter or a cold-filament load without failing on the first half-cycle. The 30 mA holding current (Ih) is moderate; the gate will drop out cleanly when the load current falls below that threshold, which matters for zero-cross switching circuits that need reliable turn-off at light load.
Gate drive and thermal design
The gate trigger current is 15 mA max, with a trigger voltage of 1.5 V max — a standard logic-level gate driver or a simple resistor from a 5 V or 12 V supply will fire it without a dedicated driver IC. The TO-220AB tab is the thermal path — bolt it to a heatsink with thermal compound; the junction-to-case thermal resistance is the number to budget for the heatsink selection.
The 10 µA max off-state leakage at 125°C is low enough that it won't push the gate drive into false triggering on a hot day.
The base product number is TYN1212; the RG suffix indicates the tube-packaged variant in TO-220AB.