I'm studying optocouplers in general, and in special the 4N25.
I'm applying the optocoupler in a zero crossing circuit, like this one:
I know the CTR is minimum of 20%, but checking the datasheet of 4N25, I'm wondering how to get the aprox. CTR based on IF and ambient temperature:
So, my question is, how to determine if is in saturation mode or not? Which curve could I look?