OPA690: output voltage

Morning Ivy, 

This is a deceptively difficult design flow as the summing junction on the inverting node has a the V+ voltage moving in the opposite direction making that series input R look like and active impedance - reducing it. I had originally worked on this in this application note, but I believe there are some errors hiding inside this one - so just look at it for an idea of the issues. I had made some progress on fixing that analysis not too long ago, it will take some time to find that and move it forward. 

https://www.ti.com/lit/an/sbaa135a/sbaa135a.pdf

This also came up in this e2e thread, I pursued it for awhile - enough to get an unlocked spreadsheet in there, but that is still the slightly off spreadsheet - and I think it is slightly off on matching the output swings on the DAC exactly, might give the right Vopp. 

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1116966/opa836-updated-complementary-to-single-ended-design-flow

In the meantime, 

1. This issue comes up so often we did the THS3217 and THS3215 where the D2S stage in that device solves this problem - it might be more part than you need, but just FYI

2. You might have the input source set up wrong, to emulate a DAC you need its common mode current then the swing around that, looks like you have bipolar input swing here, 

3. That +/-4.1V swing is beyond  what the OPA690 can do on +/-5V supplies, might want to increase the supplies to +/-6V or reduce your targets. 

And that depends on load as well, 

Ok Ivy, I made some progress on this using that unlocked original spreadsheet. I had to change some things to get a solution, 

1. I targeted lower gain, 180ohm on each side which should give a +/-3.6V output

2. I had to target a higher impedance looking in, 40ohms here that will still hold the DAC output swing below its max compliance, 

Actually works pretty well - the output swing is right on, the inputs voltages have slightly different swings (above ground) as expected - but not much, the key was that red max gain cell, must be greater than the target which is what led me to reduce the target gain trying a number of combinations. 

And this file which also has the corrected DAC source current model - that is a 1MHz signal above, 

OPA690 Comlementary DAC interface.TSC

And here I went ahead and pushed this to the full +/-4.096V swing assuming an increased supply is ok, had to increase the input impedance to 50ohm but that is still ok I think, 

OPA690 Comlpementary DAC interface updated.TSC