V G wrote:
> they seem to have
> made their own instrumentation amplifier that looks like this

There is no special magic to making a diff amp with a fixed known gain
(instrumentation amplifier).  You can certainly make your own.  However, to
get the same kind of common mode rejection ratio in your discrete circuit
that is available in a pre-packaged unit takes part tollerance matching
beyond what you can reasonably achieve.  In other words, you won't be able
to achieve the same common mode reject they can.


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