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AD627 supply when at lower rail exceeds 85uA maximum

Question asked by tomclary on Oct 20, 2015
Latest reply on Oct 22, 2015 by harryh

I'm using the AD627 to subract a DC bias in a very low power application.  The data sheet says 85 uA supply current maximum.  Which seems true for positive differences all the way up to the positive rail.  I'm seeing like 180uA when the difference is negative and the output is going to ground.

 

This is being used with a single 5V supply and the gain resister is 18K.  I've measured 47uA going through the gain resister in this situation and that is subtracted out.

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