Notice that U54 isn't in there yet. That's one of the 4 HCPL-4506 optocouplers. The datasheet says that the propagation delay variation from part to part is as much as 500nanoseconds...:
Fran said that it was probably less than that... Well, as usual, he was right, but he didn't realize how right he was:
Turn off delay was about 45 nanoseconds before it got the memo to go down.
Here's a DIFFERENT hcpl-4506. Maybe a delay of 46? hahaha:
Like 85-90 nanoseconds before it starts to turn on.:
And a different one for turn on:
Man, these things are the same within like 5 nanoseconds or something. That's 5 billionths of a second. I think the mosfets can handle being turned on with a difference of 5 billionths of a second. haha.