Before I suggest a suitable op amp to drive an ADC, I look at the application. This steers me toward one of two categories: low voltage or high voltage.
If the system requires a low voltage operation, chances are I’ll look for a low power op amp. Depending on how low the power needs to be, I may also look at a few different options in addition to the input stage and the building process. That’s because not all low voltage op amps have a CMOS input stage. Conversely, if the application is sensitive to noise and the goal is to optimize for dynamic range, I’d look at the 30-V or higher, such as the OPA211 , though sometimes 24-V like the LM6211 will work. But, this isn’t enough.
You also need to consider the output drive capability of the op amp. This can lead to some reluctance, especially in low power designs, as you may think that your micro power amp will never have enough juice to drive the input stage of your ADC. In reality though, it comes down to the biasing and the design of that particular amplifier. Some have a very robust output drive even with very little quiescent current, such as the LMP2231. This is where design talent comes into play; it depends on how much of the bias current is diverted to the output stage.
Of course all along you’re also looking at the DC specifications of your op amp to make sure you stay within the acceptable boundaries of the design. But how many people look at things like settling time, I wonder! This is an important parameter, and can really hurt your conversion time if you’re not careful.
I sometimes hear someone say “oh, no problem with settling time, I just look at the widest possible bandwidth and I know that will have a faster settling response.” Well yes and no.
Yes, because bandwidth gives an indication. No because it isn’t enough. What settling time also depends on phase margin as well as the location of the poles and zeros, be them intrinsic to the op amp or external.
So next time you’re looking to take a driver out for spin check out the OPA320, settle within 0.5us at 16 bits and use it with the ADS8319. You’ll be the first one to the checkered flag!!