The H11A2S is officially listed as Obsolete by onsemi, meaning it is no longer manufactured in volume and has no direct factory replacement from the original manufacturer. Sourcing this part today means going through independent distribution channels — surplus inventory, broker networks, or end-of-life stockpiles. Availability and pricing are lot-specific and confirmed at RFQ time.
5300Vrms isolation voltage means this opto can withstand a 5.3 kV transient between input and output without breakdown — a standard rating for reinforced insulation in mains-referenced circuits like motor drives, power supplies, and PLC I/O modules. 20% minimum Current Transfer Ratio (CTR) at 10 mA forward current sets the gain floor: at 10 mA input, the output transistor will sink at least 2 mA. For a typical 5V logic load with a 2.2k pull-up, that 2 mA is enough to pull the output low — but the 20% minimum means the design must budget for the worst case, not the typical 50-100% CTR. 2 µs turn-on and 2 µs turn-off times place this part in the medium-speed class — fine for 50/60 Hz line sync, relay drivers, and status feedback, but too slow for high-speed data links or switching power supply feedback loops above ~50 kHz. The transistor-with-base output gives you access to the base node — useful for tailoring the switching threshold with an external resistor, or for driving a Darlington pair without an extra opto.
Package and board fit
The -55°C to +100°C operating range covers industrial temperature environments — fine for factory-floor control cabinets, but the upper limit sits below the +105°C or +125°C grades needed for under-hood automotive or high-density power supplies. The 30V output maximum and 400mV Vce saturation mean the output side can switch 5V, 12V, or 24V logic levels cleanly — the saturated voltage drop of 0.4V is well below the logic-low threshold of most digital inputs.