4N28SM

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Optoisolators, also called optocouplers, are devices used to physically isolate two parts of a system that still need to communicate with one another. This ensures that, even when problems or malfunctions happen in one part of the system, the other(s) remain unaffected. In particular, optoisolators are used in situations where sensitive signals need to be passed from one section to the other without any interference that could be caused by existing electrical connections. One example is where AC mains signals must be isolated from a low-voltage control circuit.

4N28SM is an optoisolator that works by combining the use of a light source, usually an LED, and a light detector, usually a phototransistor, together in a single package. An electrical signal is applied to the LED and the LED emits light. This light is then detected by the phototransistor detector, which then produces an electrical output in response, essentially isolating the electrical signal. The datasheet for the 4N28SM optoisolator lists it as a transistor, photovoltaic output optoisolator. This indicates that the electrical output is of a discrete, off-on type that is capable of switching AC and DC signals.

For the 4N28SM, the main application fields are in telecommunications, computers and factory automation systems. These applications typically use the optoisolator to protect delicate or sensitive electronic equipment from damage caused by fluctuations in voltage or current. In particular, they are used to isolate analog voltage signals from digital signals, or digital signals from AC mains signals.

The working principle of the 4N28SM optoisolator is relatively simple. It consists of an LED light source which is powered by an electrical signal, usually between 1V and 6V. The light generated by the LED is picked up by the phototransistor detector, which then produces an electrical output in the form of an ON/OFF type signal. This electrical output is then used to switch an external load, like a relay or a triac. The amount of current used by the LED is much lower than that used by the load, which ensures that the load will not be affected by any fluctuations in the LED’s current.

The 4N28SM optoisolator, much like any other optoisolator, offers a high degree of electrical isolation and noise immunity. It is highly reliable and is easy to implement in a variety of applications. In conclusion, the 4N28SM optoisolator is a robust, reliable solution for isolating electrical signals and protecting delicate electronic equipment from damage.

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