12-5 PUBLIC

Switch SW1 closes at t=0. Circuit is in equilibrium just before t=0. Opamp OA1 is ideal. I'm have trouble calculating the time constant for the capacitor's waveform. Can anyone help?

VM1 = (-Rf/Ri) x { [ (Vi-Vf) e^(-t/T) ] +Vf}

I have Vi as 0v, and Vf as 2v. t is time, and T is tao (time constant).

To find T, T = R(across capacitor) x C(uF)

I am calculating Rc as 2, but I am not sure if that is correct, because that only incorporates R1 and R2 (in parallel) in series to R3 (aka Ri). I cannot figure out if R4 (aka Rf) should be incorporated into the R thevenin of the capacitor.

Please help!

Not provided.