How to calculate gain of diff amp

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karnel

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Can someboby give a quick tip how to calculate gain of such type diff amp?
 

To me it looks G = (R3+R4+R5)/R3
Right?
 

You schematic is incomplete. You have 2 inputs and 2 outputs ! There should be one more stage on the output side.
 

hi
i think the circuit you used is int the file, a ic finished included your circuit.
 

The calculation is rather simple:

*For ideal opamps the difference between both input signals (Vin1 and Vin2) is identical to the voltage across R3 (because the voltage between the opamp (+) and (-) terminals is practically zero).
* When the difference between both output voltages is called (Vout1-Vout2) there is a simple voltage division between both differences:

Vin=(Vin1-Vin2)=R3/(R3+R4+R5)*(Vout1-Vout2).

* Thus the gain (Vout1-Vout2)/(Vin1-Vin2)=Vout/Vin=1+(R4+R5)/R3
(as given already by KARNEL in his answer).
 

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