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As the ideal op-amp circuit shown in Fig.4-3, determine the circuit voltage gain Uo/Us. https://courses.edx.org/c4x/TsinghuaX/20220332X/asset/4-3.PNG
To find the solution to this problem requires two other properties of a ideal Op-Amp, output impedance is zero and the differential input is zero. With this you can determine VA with superposition for Us, U1, and Uo and then set equal to zero. You can also determine how U1 is related to Uo. Solve for Uo and then divide by Us.