AC/DC input optocoupler with 4170Vrms isolation
The H11AA1SR2M is a single-channel optocoupler from onsemi that accepts both AC and DC input — a feature that eliminates the external bridge rectifier when sensing AC line voltage or detecting zero-cross events. Output is a phototransistor with base access, giving the designer flexibility to bias the transistor for speed or to use the base as a logic-level trigger. Rated for 4170Vrms isolation, it suits reinforced insulation in mains-referenced circuits such as switch-mode power supply feedback, PLC digital input modules, and motor-drive status monitoring.
Transistor output with base access
The output transistor is rated for 30V maximum collector-emitter voltage and 50mA continuous output current, with a typical Vce saturation of 400mV at the rated forward current — enough margin to drive a logic gate input or a low-power relay directly. Minimum current transfer ratio is 20% at If=10mA, meaning the output transistor can sink at least 2mA when the LED is driven at 10mA. This CTR floor is the key parameter for ensuring the optocoupler pulls the output low reliably across temperature and LED aging. The base terminal is brought out, allowing a base-emitter resistor to speed up turn-off or a base-drive capacitor to tailor the switching response — a feature not available on simpler two-pin phototransistor optocouplers.
Active production, surface-mount reel packaging
onsemi lists the H11AA1SR2M as Active. The package is ROHS3 compliant.