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interfierence with infinite gain op amp

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ACTUALLY WHAT I WANT DO IS THIS.
I NEED TO MAKE A SENSOR TO DETECT WHITE SURFACE IN BLACK BACKGROUND.SO WHAT I THOUGT WAS BY EMMITING RED LIGHT TO BOTH SURFACES,WHITE WILL REFLECT WHILE BLACK WILL ABSORBE LIGHT.SO IN SENSOR I THOUGT IF LED GENERATES VOLTAGE WHEN RECIEVING LIGHT I CAN USE IT HERE COZ WHITE SURFACE WILL REFLECT LIGHT AND SENSOR LED WILL GENERATE FEW mv WHEN IT RECIEVED THIS REFLECTED LIGHT FROM WHITE SURFACE.SINCE BLACK SURFACE WILL ABSORB LIGHT SENSOR WILL NOT GENERATE ANY VOLTAGE.
SINCE GENERATING VOLTAGE IS LOW AND HAVE ONLY TINY CURRENT I THOUGT FET BASED OP AMP WILL SUIT THIS.BECUSE FET DOES NOT REQUIRE INPUT CURRENT.AND SINCE I WANT DIGITAL OUT(WHITE SURFACE OR NOT) I PUT POTENTIOMETER TO POSITVE INPUT TO SET REFERENCE VOLTAGE.
AND SET SENSOR LED IN REVERSE MODE(positive pin to negative supply and negative pin to inverting input pin).
SO IF VOLTAGE GENERATE ON LED BY REFLECED LIGHT IS LARGER THAN REFERENCE VOLTAGE OP AMP OUTPUT WILL BECOME LOW.OTHERWISE IT WILLBE HIGH.

ACCORDING TO THIS I DESIGN ABOVE CIRCUIT.
SO TELL ME WHATS WRONG WITH IT.
THANKS
 
The inputs of a TL084 and a 741 opamp do not work when they are less than 3V above the negative supply voltage that is 0V in your circuit. Both inputs of your opamp are less.

The minimum supply voltage for a TL084 is 6V to 7V and many 741 opamps do not work if their supply voltage is less than 10V.
 
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