Stephan Boettcher wrote:
And since I do not have much experience with GHz class opamps, I tend to
put the parts rather too close than too far apart. I do not want an
oscillator there.
Some recent work at my day job involved 400 MHz opamps. These things
require careful layout to keep from oscillating, just as you say. The
vendor (TI, I think) recommends removing copper on all layers around the
input pins. Trust me, this works. One board accidentally removed the
cutouts, and the opamp sang like a soprano. Other stuff that is pretty
good practice is to place a series 10-Ohm resistor on the output of the
amp. You can always zero it out, but it gives you the chance to
decouple the output from the input - especially if you are running unity
gain. Watch that phase margin!
And since we want to sample with 14-bit resolution, I
do not want too big antennas on the input circuits either, to pick up
digital noise from the back end.
I suggest to follow the current path, from opamp vcc/vee to load, and
back to opamp. Be sure the return path is not through the supply,
possibly off the card.
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