AVR-Chat

--- In AVR-Chat@yahoogroups.com, Dave VanHorn <dvanhorn@d...> wrote:

> ... dual-optoisolator, and an opamp,
> to implement a modem hybrid without
> any transformer ...

What happened to the DC wetting current of the line?  Was that 
carried over the isolation barrier to?  Was the op-amp circuit line-
powered? What bit rate or modem standard did this work with?

I worked on this kind of stuff too. To avoid the non-linearity of wet 
transformers I picked off the wetting current in an active circuit 
and AC-coupled to a dry transformer. Expensive! Now, years later, I'm 
working on SONET. 622 Mbit/s. Hey, that's optically isolated too!

Graham.