It is the standard values of current handling capacity specified to a phototransistor output of the optocoupler, which may range between 40 to 100 mA. Rise/fall time: This parameter defines the logical speed of the optocoupler response across the internal IR LED and the. In addition to the absolute maximum rating for the "Phototransistor: Collector Current (I C)", when a collector current (I C) that exceeds the value obtained by dividing this value by the collector-to-emitter voltage (V CE), destruction or non-recoverable degradation may occur. The allowable. Optocouplers (also known as optoisolators) are electronic components that provide electrical isolation between input and output circuits while allowing signal transfer via light. As an isolator, an optocoupler can prevent high voltages from affecting the side of the circuit receiving the signal. PC817 and TLP521 are key references, used in control, power and isolation. Optocouplers are essential elements in.