I am trying to calculate the gain Vout/Vin of the circuit below. I'm not really sure where to start, can anybody help?

enter image description here

  • 1
    \$\begingroup\$ You should have a look at this(49m:31s) video by Dave Jones where he explains what an op-amp is and how it works. It helped me when none of my teachers could get down on my level. \$\endgroup\$ Commented Feb 28, 2018 at 7:17
  • \$\begingroup\$ The currents into the + and - op amp terminals are both zero, hence the R1/C1/R2 series circuit is a voltage divider across Vout and ground (0V). The other relationship you need relates the op amp input voltages: V- = V+ ; then you can derive and equation for Vout/Vin \$\endgroup\$
    – Chu
    Commented Feb 28, 2018 at 8:10
  • \$\begingroup\$ Start by labelling Vin and Vout. \$\endgroup\$
    – Andy aka
    Commented Feb 28, 2018 at 8:49
  • \$\begingroup\$ Given finite common-mode rejection, is this not a potential oscillator? \$\endgroup\$ Commented Feb 28, 2018 at 14:31

1 Answer 1


Assume that:

  • no current flows into the input of the opamp
  • the input voltages of the opamp are the same

Then write down and solve the Kirchoff equations.

  • \$\begingroup\$ Will the input voltage of the op amp be Vin or will the point between C1 and R2 be Vin? \$\endgroup\$
    – gene
    Commented Feb 28, 2018 at 6:54
  • \$\begingroup\$ The + and - signs in the opamp symbol denotes its inputs. \$\endgroup\$ Commented Feb 28, 2018 at 7:02

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