Integrators and Differentiators

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Discussion Overview

The discussion revolves around the accuracy of simple series RC circuits as integrators and differentiators compared to operational amplifier (opamp) designs. It explores the theoretical underpinnings, practical limitations, and the impact of load on circuit performance.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant questions why RC circuits are considered less accurate integrators/differentiators than opamp designs, despite the mathematical derivations suggesting ideal behavior.
  • Another participant explains that the high input impedance of opamps allows RC circuits to operate more ideally, while also providing low output impedance for driving subsequent stages.
  • A participant acknowledges the role of buffering in opamps and suggests that the RC constant in an RC circuit varies with load, affecting its integration accuracy.
  • A later reply confirms that the load impedance affects the RC circuit's output, altering its frequency response and integration characteristics.

Areas of Agreement / Disagreement

Participants express agreement on the influence of load on the RC circuit's performance, but the overall discussion remains unresolved regarding the extent of accuracy differences between RC circuits and opamp designs.

Contextual Notes

Limitations include the dependence on load conditions and the assumptions made in the mathematical models of the circuits, which may not fully account for real-world factors.

TheAnalogKid83
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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?
 
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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.
 
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.
 
TheAnalogKid83 said:
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.
 

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