Common causes of optocoupler failure include excessive heat, improper voltage or current levels, and damage to the LED or phototransistor. Incorrect soldering, or the use of unsuitable components in the surrounding circuit, can also contribute to optocoupler failure. Their performance hinges on proper biasing and integration within the feedback control loop; misconfiguration can lead to instability, poor. I have got an optocoupler to switch an output between 0V and 3. That output is also inverted with a NOT gate, but for simplicity, we could focus on just Out_Enable1 signal. As far as I understand, I must read a logic 1 (3. 3V aprox) when I set GND in Signal1 input. I am. TI's TL431 contains both an error amplifier and reference.