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Of Analog Signal Filtering


Some intuition about this topic can be developed without summoning the ghost of Pierre-Simon Laplace.

In principle, the relative simplicity of these circuits should make the underlying theory easy to self-study; in practice, most introductory texts rapidly devolve into a foul mix of EE jargon and calculus. To test this in practice, let’s assume R = 10 kΩ and C = 1 µF; as per the formula, 50% charge should be reached in ~7 ms. And indeed, we can easily observe this by supplying a 5 Hz square wave on the input leg: Now the fun part: recall from the discussion of impedance that a capacitor in the presence of a sine wave signal exhibits behavior that resembles frequency-specific resistance.

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