Revision 5 of a datasheet for the 4N25 optocoupler, a 281 KB PDF. The 4N25 is one of the oldest and most common phototransistor-output isolators, often found in power supply feedback, PLC inputs and appliance control boards. The document gives the standard six-pin layout, electrical characteristics, transfer ratio curves and isolation ratings needed when testing a suspected faulty part or choosing a substitute. Different vendors publish their own sheets, so compare with the brand marked on the component.
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