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AD7684 issue (strange behavior)

Question asked by WintonM on Nov 8, 2012
Latest reply on Nov 9, 2012 by harryh



We are trying to modify the input stage of an already manufactured board by replacing AD7793 by AD7684 in order to measure up to 1KHz signals. I have attached a simplified schema of our input stage and two waveforms we have obtained from the AD7684 output.


We are only getting good performance when we connect our oscilloscope to IN+ and IN-, furthermore, we get good results when connecting just the GND of the oscilloscope wherever IN+ or IN-.


We need to measure in both scenarios IN+ > IN- and IN- > IN+, that is why we selected this AD7684 truly differential instead of AD7693


Could you provide some solutions, similar experience... any hint could help!


Best regards and thank you in advance,