== An Analog Integrator Macromodel ==
[[Image:Integ1.png|thumb|400px|A practical voltage integrator circuit using an Op Amp.]]
A practical voltage integrator circuit using an ideal Op Amp is shown in the opposite figure. The voltage transfer function of this circuit is given by:
which represents a integral operator in the Laplace s-domain. This circuit is very similar to the Op Amp differentiator except for the fact that the timing resistor and capacitor have switched places.
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[[Image:Integ1.png|thumb|left|640px|A practical voltage integrator circuit using an Op Amp.]]
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An equivalent macromodel of the above circuit is given in the following figure, which represents RF.Spice's "Analog Integrator Block". In this model, the ideal Op Amp has been replaced with the linear controlled voltage source E2: