After reading a lot of app-notes and datasheets, and some pretty nice AnalogZone documents from TI I have a better understanding on how all this SAR ADC's work and how to buffer their inputs, but I can't seen to find a nice rail-to-rail input and output op-amp that doens't have crippled Vin common mode voltages, they are all limited to 1 or 2v in the best cases, and usually only about 300mV differential inputs are allowed.
I will go the single ended route for now, it seems a bit easier and the trully diffferential op-amps are very limited in choice.
So I'm asking for some good to use op-amps.
And I would like to have a sanity check.
Based on this:
![](http://i.imgur.com/pTTsE.png)
I can set my common mode voltage to 2.5v, and then use a 2.048v reference so I dont need to really hit the rails when driving the ADC, because even rail-to-rail op-amps dont have perfect drive capabilities near the rails.