Isolation and signal transfer for legacy designs
The H11A5100 is a 1-channel optoisolator from onsemi, designed for DC input and transistor-with-base output. It provides 5300 Vrms of galvanic isolation between input and output, suitable for breaking ground loops and protecting low-voltage logic from high-side transients in industrial or power-supply feedback paths. With a minimum current transfer ratio of 30% at 10 mA forward current, the part guarantees a known output drive level for a given LED current — critical for maintaining the logic threshold over temperature and LED aging. The 30 V maximum output voltage and 400 mV Vce saturation define the load-side swing and headroom.
Sourcing reality for a discontinued part
For a board spin or new design, a functionally equivalent optoisolator in the same 6-DIP footprint with matching 5300 Vrms isolation and similar CTR would be the migration path — the H11A family shares the base pinout, but each suffix has unique CTR and switching characteristics that must be verified against the original application.