You mentioned rail-to-rail output. Is the AD8422 intended for single-supply applications?
The AD8422 works on a wide range of supplies from +4.6V single supply to ±18V dual-supply, providing excellent power-savings and high-precision performance regardless of the supply voltage. The AD8422 is designed for high performance at high or low supplies, but is very useful in systems that need a single-supply. The rail-to-rail output of the AD8422 greatly improves the achievable dynamic range in low supply voltage applications, and the preamplifiers are also
rail-to-rail, which improves the common-mode range.
AD8422 has much better noise and bandwidth characteristics than existing single-supply instrumentation amplifiers such as the AD623 and the AD8226. It is, however, important to note that because of the structure of the input stage, the AD8422 input range does not include ground, so it is not appropriate for single-supply applications that measure at ground.