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Problem with icl7107 and opamp

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vukhanh97na

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Hello everybody . I'm newbie in here. I have a trouble when i work with icl7107 and opamp . I don't know how to fix this problem .
Can anybody please help me ? 1.PNG
 

Hi,

Too lazy to write an error description?

Klaus
 

oh , sorry . I forgot it .
the icl7107 works well when i use Vsource ( as new images ) . but when i use op amp , it don't work . I don't know how to fix that .
sorry for english .6.PNG
 

Review FvM`s remark on post #3.
You are supplying ICL7107 at pin V- with 0v, whereas should be -VDD.
 
You should really read the datasheet thoroughly, study the block diagram and application circuits.

You can either tie GND to V- or GND to Vin-, but not both.
 
Hi,

Have you looked at the op amp output range and checked to see if it's exceeding the 7107 input range in some way?

I don't see why it would be that though, the 7107/7106 are 200mV or 2V input as far as I recollect and your op amp input to the ADC is only 100mV (surely?).

- - - Updated - - -

The LM358N datasheet says input to 0V (-0.3) and input offset voltage only 3mV max, so wouldn't that only be 6mV + bit more in case so say 10mV "noise" at the output only, meaning maybe 110mV at ADC input?
 
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