[SOLVED] OpAmp AD8607 gain error

[GUMY]

I am experiencing strange behaviour of AD8607. It should be pA biass current and uV offset voltage Opamp, but simple voltage follower configuration shows this results:


Error seems to be related to source impedance as it dissapears if I connect Opamp input directly to voltage reference output (no potentiometer). But this make no sense regarding pA bias current...
I allready excluded some possible error sources:
-ground loops
-IC damage (same behaviour after replacement)
-Measuring accuracy

I am missing something, but what?

 

[FvM]

The most plausible explanation is that your multimeter has about 10 MOhm input impedance, and you switched it between input and output. You need to connect an equivalent load instead of the multimeter to get the same input voltage when the multimeter is disconnected...

To suggest a measurement trick: If you measure Vin - Vout difference directly, the input voltage loading effect will be negligible.

 

[GUMY]

Yes offcourse. Where is my mind today... Thanks FvM.