Phototriac optocoupler for AC load switching
The VOT8121AD is a 1-channel phototriac optocoupler from Vishay in a 4-DIP through-hole package. It switches AC loads up to 100 mA RMS at off-state voltages to 800 V, with 5300Vrms isolation between input and output. Typical applications include solid-state relays, AC motor starters, solenoid/valve drivers, and industrial PLC output modules where isolated triac drive is needed.
Key ratings for BOM fit
5300Vrms isolation is the standout safety rating — sufficient for reinforced insulation in mains-connected equipment per UL/VDE. The 800 V off-state voltage lets it handle 240 VAC lines with margin for surges. Non-zero-crossing output (no zero-crossing circuit) means the triac fires immediately when LED current exceeds the 10 mA max trigger threshold, making it suitable for phase-control dimming or random-turn-on SSR designs. The 400 µA typical holding current ensures the triac latches once triggered; if the load current drops below that, the triac will commutate off at the next zero-cross.
Package and approvals
Housed in a standard 4-DIP (0.300", 7.62mm pitch) through-hole package — easy to hand-assemble or wave-solder. Approved by CQC, cUL, UL, and VDE, which simplifies certification for export designs. Operating temperature range -55°C to 110°C covers industrial and some automotive under-hood environments.
Sourcing and lifecycle
No last-time-buy or obsolescence risk for current production.