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What are the different models of optocouplers

Fibre interconnection and data room reference Published 13 Oct 2026

Use this reference to prepare product questions for FD SOLUCIONES. Check interfaces, capacity, protection and installation requirements against the current product documentation.

Optocouplers are classified based on their photosensitive output devices, including phototransistor, photodarlington, photo-SCR, photo-triac, and photodiode types, each suited for specific applications.

Phototransistor Optocouplers

These are the most widely used type, where the LED inside the optocoupler activates a phototransistor to allow current flow in the output circuit. They are suitable for general signal isolation in both digital and analog DC circuits. Variations include NPN or PNP configurations, and some designs provide an additional pin to control sensitivity and reduce false triggering from noise or transients.

Photodarlington Optocouplers

A photodarlington optocoupler contains two transistors connected in a Darlington pair, providing higher current gain and sensitivity than a single phototransistor. This makes them ideal for low-power control circuits where a small input current needs to control a larger output load. Photo-SCR OptocouplersPhoto-SCR optocouplers use a light-activated silicon-controlled rectifier (SCR) as the output device.

They are designed for high-power applications, capable of handling large currents and voltages, and are commonly used to switch DC or AC loads.

The LE

D triggers the SCR, which then controls the output circuit.

Photo-

Triac Optocouplers

These optocouplers are similar to photo-SCR types but are specifically designed for AC load switching.

The LE

D activates a triac, allowing the device to control AC power efficiently. They are widely used in AC motor control, lighting, and other high-voltage AC applications.

Photodiode Optocouplers

Photodiode optocouplers employ a photodiode as the detector, offering extremely fast switching speeds. However, their current transfer ratio is typically low, often less than 1%, making them suitable for high-speed signal transmission rather than high-current applications.

Other Variants

Additional types include resistive optocouplers (photocell-based), LED-photodiode, LED-laser, and reflective or slotted optocouplers. These are used in niche applications such as audio equipment, optical encoders, and custom DIY circuits. Understanding these types helps in selecting the right optocoupler for a specific application, balancing factors like switching speed, current handling, voltage isolation, and sensitivity.

What are the different models of optocouplers - FD SOLUCIONES OPTICAL SYSTEMS [PDF]

What are the different models of optocouplers

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This reference is intended for preliminary fiber and communications infrastructure research. Optical interface, fiber type, port or core capacity, electrical input and output, enclosure protection, cooling, installation limits and applicable standards must be verified for the specific project.

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