On 3/30/2010 11:20 PM, Bob Blick wrote:
>
>> On 3/30/2010 6:29 PM, ivp wrote:
>>> Hi all,
>>>
>>> Help
>>
>
> You are exceeding the common-mode range of the opamp by having 10v/2
> going into each input.
>
> Cheerful regards,
>
> Bob
>

Doh!  I believe Bob put his finger on it.  The input device is 
attempting to raise the inputs of the amp above the power supply rails, 
and probably is causing current to flow into the input diodes.

To test this, try increasing the positive power supply enough that the 
above case is not true.  Check the input common mode range on the data 
sheet to see just how much you need to raise the supply.
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