![]() A photodiode will provide a very low output-to-input current transfer ratio compared to a typical phototransistor IC.ĭarlington pair phototransistor: These optocouplers are also useful for their high gain and they offer among the highest output-to-input current transfer ratio. These components can be used when the LED is switched with a stream of digital pulses or with an AC signal. Photodiode: An optocoupler with a photodiode as the detector is common in systems that need fast switching. ![]() However, they are also quite slow and are also best used for moderately high voltage/current DC systems. Silicon-controlled rectifier (SCR): These optocouplers also provide high gain, similar to a triac. They have slow response speed and are best for high voltage DC systems that require high current output. Triac: An optocoupler IC with a triac as the detector is used in systems that require high output voltage/current. Here are other types of optocoupler ICs you’ll find on the electronics market: Optocouplers may use other switching elements aside from a phototransistor. ![]() NPN or PNP phototransistors can be found in optocoupler ICs. This isn’t to say that they are a cure-all for every noise problem, but the isolation they provide does isolate systems at different voltages, which has a nice benefit of suppressing ground loop noise from two portions of a system. This is one way to conduct a low voltage signal into a high voltage circuit block without using an amplifier.īecause these components are inexpensive optical elements, they nicely provide electrical isolation between different circuit blocks without conducting certain forms of EMI between different circuit blocks. The LED may be running at a different level than the internal phototransistor, which allows some isolation between these two signal levels. This then turns on the phototransistor, allowing current to flow through a connected circuit. When the LED receives an input signal, the LED turns on and supplies photons to the base of the phototransistor. Very simply, an optocoupler integrates an infrared LED alongside a photodetector (usually a phototransistor) and acts like an optical switch. Here are some options for optocoupler ICs you can quickly import into your next electrical or electro-optical system. Some optocouplers are also designed to provide switching at high data rates. They are also ideal for use in feedback loops between different circuit blocks, especially where isolation is required. They are easy to bring into different circuits and nicely provide isolation between circuit blocks running at different voltages. An optocoupler IC integrates optical elements that act like a simple switch. For new designers, an optocoupler sounds like it might have little to do with electronics, but they are important devices for providing isolation between different circuit blocks.
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