Question
Are there any interesting circuits that didn’t quite make the datasheet?
Answer
AD8237 does very well on a single supply measuring small ground-referenced
signals. A great example is a thermocouple interface. A grounded thermocouple
would require a dual supply for almost all other in-amps because of the
“hexagon plot”. AD8237 can also be used on the low side to measure
bidirectional currents because of the wide input range. Another circuit that is
potentially very useful is this highly efficient precision current source.
For more than a couple mA of current a boost transistor will be necessary, but
that transistor is within the loop, so it won’t affect overall accuracy. As a
quick side note, AD8420 can be used the same way and it will have higher load
compliance because it has a wider supply voltage range. The AD830, AD8129, and
AD8130 have some interesting ideas that may be applicable too, such as a
resistor-less gain of 2. The ICF architecture opens up a world of flexibility,
and there are certainly many more useful circuits we haven’t thought of or seen
yet.
