For the circuit below, R1 = 12 KΩ, R2 = 1 KΩ. Determine the gain, G.

I have done the following:

G=(Va-Vb)/(V2-V1)
V-=V+=V2
V+=V2
I1=V2/R2
V1=(V2/R2)*R1

Va=V2((R1/R2)+1)
Va=(13)(V2)

now for trying to do the second part for V1 and Vb I am stuck.

 

You need to define your variables. You use V- and V+. But those are not on your diagram and since you have two op-amps it is ambiguous which voltages you are referring to. You also use I1 but define neither where that current is or what direction it is flowing in.

We are not mind readers and engineering is not about guessing.

Label all nodes that are not already unambiguously labeled and then any currents you refer to annotate them on the diagram. Doing this not only aid in communicating your thoughts and intentions to others (including the grader!), but they will help you think more coherently about the problem, too.

 

hi,
Look at this clip from a datasheet, it should give you a hint on how to solve the problem.
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