Re: What application that use Rail-to-Rail Op Amp ?
This question reminds me of a saying by the late Jim Williams, of Linear Technologies fame, which had a quick mind and somewhat sarcastic humor:
Jim: "On a given circuit, there are only three parameters that matter in an op-amp."
Public: "And which are those parameters?"
Jim: "It depends on your application."
Behind what on the surface appears to be a Homer Simpson-stupid response, it actually holds a key truth: the actual way that an opamp is expected to operate in a circuit, will determine exactly which opamp parameters one must be concerned with.
For the OP's benefit, the R-2-R opamps are mostly used where only a single low voltage supply (i.e. +5v or even lower) is available.