Thanks Klaus
I may experiment with other op amps but I really like the bandwidth on this ADA4817 as well as the Input impedance. I need really flat performance up to 70MHz at the front end, the signal will then be down mixed to a much lower frequency.
The resistors in this circuit will be hand picked and matched to improve CMRR and I will have to AC couple on the “ref” pin through a low resistance reed relay or similar as I don’t want to reduce the Input impedance.
I know this won’t be cheap, but I am trying to achieve high end performance.
“Trying” being the key word!
The common mode issue was an oversight but I can work with it, I feel a little silly now.
Thanks to everyone
S