50 kV isolation — the real BOM gate
The OPI150 is an active-production optocoupler from TT Electronics/Optek Technology that isolates a DC input from a transistor-with-base output at 50,000 VDC — that is not a typo, and it is the spec that decides the BOM line. For any design where the galvanic barrier must withstand high-voltage transients between the primary and secondary side, this part fills the slot. The through-hole axial 5-lead package (Supplier Device Package: Axial) is the footprint you need to match on the PCB. The scorch mark tells you if the isolation failed — but with 50 kV rated between input and output, the failure signature is usually the board around it, not the opto itself.
Parametric check for the repair bench
The output is a phototransistor with the base brought out — you can bias the base for faster switching or leave it open for standard transistor operation. Vce saturation is 500 mV max at the rated output current of 25 mA. Minimum current transfer ratio is 10 % at 10 mA forward current — meaning at 10 mA in, the output can sink at least 1 mA. Turn-on time is 120 µs typical, turn-off 70 µs typical, so this is not a high-speed digital isolator; it is sized for DC-level sensing, fault feedback, or slow analog signals across a high-voltage barrier. Operating temperature range is -40 °C to 85 °C, covering industrial and outdoor equipment enclosures. ROHS3 compliant, so no exemption paperwork needed for EU-market builds.