An optocoupler transfers information using light while keeping two electrical sides separated. That does not mean every device handles the same signal, speed or safety function. Phototransistor, logic-output and gate-driver optocouplers are different components.
Check these eight points
- Function: simple status, analogue transfer, fast data or gate drive?
- Input: determine LED current, forward voltage, tolerance and dissipation.
- Output type: phototransistor, Darlington, logic gate, triac output and driver behave differently.
- CTR: check the minimum at current, temperature, ageing and required collector current.
- Speed: assess propagation delay, rise/fall time, saturation and switching frequency.
- Isolation: distinguish test isolation voltage, continuous working voltage and insulation class.
- Distances and package: creepage, clearance, pinout and PCB layout form part of the safety path.
- Environment: temperature, common-mode transients and lifetime can change the margin.
A high typical CTR is not a guaranteed minimum transfer. Design with minimum and maximum values under relevant conditions and avoid unnecessary transistor saturation in fast switching.
An isolation-voltage rating is not permission to use a device at mains voltage. Have a safety-critical design reviewed by a qualified expert.
View optocouplers and verify the exact datasheet, insulation category and applicable safety conditions.