Optocoupler is an electronic component that has a light source at its input side and a light detector or sensor in its output side. A light source is a LED while the detector or sensor is a phototransistor. It is also called as optoisolator, photocoupler or optical isolator. This device is considered as a current controlled current source. This is
Current transfer ratio is comparable to BJT’s HFE or beta (β). This is the ratio of the optocoupler’s collector current to the forward current. Current transfer ratio is popular by its abbreviation CTR. CTR is simply the measure of the optocoupler’s transfer efficiency. If we recall the basics, optocoupler is a semiconductor device with a light source and a detector.
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