I checked the AD8418 and A datasheet.
Those are almost same, but those actual features seems a little different.
What feature has improved?
I checked again. Figure 3 to 25 are totally different. Slew rate , Gain vs Freq, bias current and output sink current etc... Sorry, I misunderstood. Those are totally different circuit, I think. How come those are same name? Please tell us how to select A or non A. Those are for different application? Regards moto
Apart from the changes in the spec, the main difference between the AD8418 and the AD8418A is that the AD8418A has a faster common mode settling time. You can check Figure 18 of both parts. Notice that for the AD8418, it takes a little over 2us to settle, while for the AD8418A it takes less than a microsecond. I would say that if you have an application where the common mode changes quicker than usual, the AD8418A would be the better choice.
I hope this helps!