Optocouplers / Photocouplers

About Optocouplers / Photocouplers

Optocouplers transfer electrical signals across a galvanic isolation barrier by combining a light-emitting input with a photosensitive output. They help separate grounds, break noise paths, protect low-voltage control circuits, and provide feedback across hazardous voltage domains in power supplies, industrial controls, motor drives, communications equipment, appliances, and automotive systems. Output types include phototransistor, photodarlington, logic-gate, photovoltaic, photo-SCR or triac, and linear analog structures, each suited to different speed, gain, and load requirements.

Select an optocoupler by isolation voltage, working voltage, creepage and clearance, insulation class, channel count, input forward current, and output type. For phototransistor devices, compare current transfer ratio (CTR), CTR bin and aging margin; for digital parts, check data rate, propagation delay, pulse-width distortion, jitter, and common-mode transient immunity. Confirm output voltage and current, switching behavior, temperature range, package, safety approvals, and reinforced or basic isolation requirements. Similar pinouts do not guarantee equal insulation, CTR, speed, or regulatory suitability.