Integrators and Differentiators

[TheAnalogKid83]

Why is a simple series RC circuit considered a less accurate integrator/differentiator than an opamp design?

I know many real world reasons like stability, but the physics differential equations seem to derive into a perfect integrator or differentiator, so why are they not so perfect despite the mathematics?

 

[berkeman]

Welcome to the PF, 83. The main difference is the very high input impedance of the opamp inputs. This let's the RC circuit operate more ideally, and still have the output signal be low impedance to drive the next stage (whatever that is). The "buffering" effect of the opamp (high input impedance, and reasonably low output impedance) is the difference.

 

[TheAnalogKid83]

alright, I figured it had something to do with buffers and driving a signal, which is basically anything to do with an opamp.

So an RC circuit's RC constant is going to change depending on its load, to where it's integration constant is not accurate?

Thanks for the explanation too.

 

[berkeman]

So an RC circuit's RC constant is going to change depending on its load, to where it's integration constant is not accurate?

Correct. When you write the KCL for the RC circuit, the load impedance draws a current out of the RC circuit's output node, right? That extra load term changes the frequency response.