In integrated circuits it's difficult to built real physical inductors but it's easy to built capacitors. So in an application that require inductors we can simulate them using only capacitors, resistors and op-amps.
The following circuit shows the topology that we can implement using an op-amp, a resistor and a capacitor in order to have a simulated functional inductor.
The inductance value of the simulated inductor comes from the product of the two resistors and the one capacitor (L=R1*R2*C).
For more accurate simulations we usually choose R1 (series resistor) to be much smaller than R2 (parallel resistor).
