The diagram above shows the pinout diagram of the typical optocoupler in DIP package. At the finish, the lead-frame pin terminals are neatly bent downward. The complete assembly is finally molded in a light proof epoxy resin forming the DIP package. Once the conductive connections are established between the die case and the appropriate lead-frame pins, the space surrounding the IR LED and the phototransistor is sealed within an transparent IR supported resin which behaves like a "light pipe" or optical wave-guide between the two IR devices. The respective pinout of the DIP are correspondingly developed from the outer branches. The isolated substrates which is included to reinforce the device are created with the aid of the inner branches. The lead-frame is in the form of stamping carved out from fine conductive sheet metal having several branch like finishing. This IR signal falls on the adjacent photodetector which is normally an NPN phototransistor (having a sensitivity set in the identical wavelength), and it instantly conducts, creating a continuity across its collector/emitter terminals.Īs can be seen in the image the IR LED and the phototransistor are mounted on adjacent arms of a lead-frame. When the terminals connected with the IR LED is supplied with an appropriate forward biased voltage it internally emits an infrared radiation in the wavelength of 900 to 940 nanometer range. The above figure shows a dissected view of a typical six pin dual-in-line (DIP) optocoupler chip. These two complementary devices are hermetically embedded in an opaque light proof package. This IR LED is optically coupled to an adjacent silicon photo-detector device which is generally a photo-transistor, a photodiode or any similar photosensitive element). Internally an optocoupler contains an infrared or IR emitter LED (normally built using gallium arsenide). Optocouplers become an effective replacement for relays, and for transformers for interfacing digital circuits stages.Īdditionally, Optocoupler frequency response prove to be incomparable in analog circuits.
Optocoupling devices work as logic level changeovers between two circuits, It has the ability to block noise transfer across the integrated circuits, for isolating logic levels from high voltage AC line, and for eliminating ground loops. Optocouplers become specifically useful where an electrical signal is required to be sent across two circuit stages, but with an extreme degree of electrical isolation across the stages.
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