Operational amplifier (non-inverting configuration

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This is a model for an operational amplifier in the non-inverting "follower" configuration (with Eplus as the input voltage). Typically the open loop gain A and the differential input resistance Rin are fixed by the choice of operational amplifier. This model requires an iterative solution; the "guess" variable can be Eout or Eminus.

In the example variable sheet shown below, a non-inverting amplifier with a closed-loop gain of 1000 is simulated. With R2=100KOhms, the model predicts that R1 must be 99.098107 Ohms. Note that the effective input resistance of the amplifier (from Eplus to ground) is 100 MOhm, much greater than the differential input resistance (between the inputs) of 1 MOhm, due to the negative feedback. 

Variable Sheet
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St Input     Name    Output    Unit      Comment
             Eout    1         volts     Output voltage (volts,mV,µV)
   100000    A                           open loop gain (unitless ratio)
   1         Eplus             mV        non-inverting input (volts,mV,µV)
             Eminus  .99       mV        inverting input (volts,mV,µV)
             Iin     .01       nA        differential input current (Amps,mA,µA,n
   1         Rin               MOhms     differential input resistance (Ohms,KOhm
             R1      99.098107 Ohms      resistor from - input to ground (Ohms,KO
   100       R2                KOhms     feedback resistor (Ohms,KOhms,MOhms)
             Zin     100       MOhms     effective input resistance (Ohms,KOhms,M
             I1      .00000999 Amps      Current in R1 (Amps,mA,µA,nA)
             If      .00000999 Amps      Current in R2 (Amps,mA,µA,nA)
   1000      Gain                        Closed loop gain (unitless ratio)


Rule Sheet
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S Rule
  Eout=A*(Eplus-Eminus)   "Basic op amp equation
  Eminus=Eout*R1/(R1+R2)  "Voltage divider feedback to Eminus
  Iin=(Eplus-Eminus)/Rin  "Ohms Law for differential input resistance
  Zin=Eplus/Iin           "Ohms Law for effective input resistance
  I1=Iin+If               "Kirchoff's Law for current
  Eminus=I1*R1            "Ohms Law for R1
  Gain=Eout/Eplus         "definition of closed loop gain