Hi,

When reviewing the datasheet for the 4n35 optocoupler, I came across a minor difference in test parameters for DC current transfer ratio. I've included the datasheet, notice the addition of a temperature parameter where the ratio is reduced by half (typical).

1)Vce = 10V, If = 10mA

2)Vce = 10V, If = 10mA, Ta = -55 to 100C

What is the first case telling us? Why is it included? What is Ta (TsubA)? What transfer ratio can I expect under normal operation?

Regards,
Mark

 

What is the first case telling us? Why is it included?

It's telling you that a conservative design would use a CTR of 40 or less.

What is Ta (TsubA)?

Ambient temperature.

What transfer ratio can I expect under normal operation?

40 and that will degrade over time.