Re: High speed driver for driving large number of lines simultaneously
Why would you use an opamp for a digital circuit? And Darlingtons tend to be slow. Why don't you use a DIGITAL device in your DIGITAL circuit??
There are lots and lots of drivers/buffers out there. You may want to use several drivers rather than trying to drive all 256 lines with a single driver. Your selection will depend on available voltages, etc. For starters, look at something like a 74LV244.
Also, you've got a signal with 10nS rise time, but you want a maximum of 12nS propagation delay? That might be a problem.