The isolation voltage is the maximum rated voltage difference that can be present between the LED and the light sensor. If in doubt, study the data sheet. The image below shows the typical circuit diagram for an optoisolator or optocoupler with inputs on the left and outputs on the right.įor the moment, we want to focus on the different types of optoisolators. When choosing an optoisolator, the key parameters to consider are the isolation voltage, bandwidth, linearity, current transfer ratio, and power requirements. There are also different optoisolator speeds, and fast optoisolators like a solid state relay will outperform something like a diode optoisolator in terms of data transfer. Don’t be surprised if you see exceptions to this convention. It’s worth mentioning that the terms optocouplers and optoisolators are often used interchangeably however, the usual convention is that optocouplers are devices that can isolate voltages of up to about 5000V while optoisolators are devices that can isolate voltages of over 5000V. Important Specifications When Choosing Opto-isolators They are particularly useful where long data cables that could be susceptible to induced voltage transients or ground plane surges enter an electronic device containing sensitive semiconductor components. There are many different types of optoisolator circuits that are widely used in communications, control, and monitoring systems where data signals could provide a point of ingress for harmful voltages to damage a device. The components are sealed in an opaque package to prevent interference from external light. This provides a barrier to any voltage transients or overvoltage levels that appear at the input from affecting the electrical circuit at the output of the optoisolator. Then, within the same device, a light-sensitive device such as a photodiode, phototransistor, or photodarlington transistor converts the light signal back into an electrical signal. In simplest terms, an optoisolator works by taking an input electrical signal and converting it into a light signal using a light-emitting diode, generally operating in the near-infrared spectrum. Opto-isolators act as a protection mechanism, ensuring that harmful electrical currents cannot flow across the device. Because there is no need to directly pass voltage or current between the inputs and outputs in an optoisolator circuit, these components can be used to provide electrical isolation in two regions in a PCB. An optoisolator is an electronic device that can be used to pass information between a diode without passing an electrical current.
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