Hi I have just started studying about amplifiers (op amps). It has been two days I cannot figure out how can you get an amplification if you have the same size inputs.

Let say I have V1 input of 5v and open loop amplification is very high, so that the gain of all circuit is determined by G=1/B passive attenuator (negative feedback). So if I want to have G=100 I would need two resistors with ratio 1:99 or lets pick 1k and 99k ohms.

So V2 is determined by negative feedback. V2= Vout x 1k/(1k+99k)=[Vin x G] x 1k/(1k+99k)=

=5 x 100 x 0.01=5V.

So the V2=V1 when the negative feedback is used. I do not understand how can op amp can amplify a signal when two inputs are the same:

V1=V2 then Vin is V1-V2=0 so 0 x G equals 0 v output.

Thank you for help

Let say I have V1 input of 5v and open loop amplification is very high, so that the gain of all circuit is determined by G=1/B passive attenuator (negative feedback). So if I want to have G=100 I would need two resistors with ratio 1:99 or lets pick 1k and 99k ohms.

So V2 is determined by negative feedback. V2= Vout x 1k/(1k+99k)=[Vin x G] x 1k/(1k+99k)=

=5 x 100 x 0.01=5V.

So the V2=V1 when the negative feedback is used. I do not understand how can op amp can amplify a signal when two inputs are the same:

V1=V2 then Vin is V1-V2=0 so 0 x G equals 0 v output.

Thank you for help

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