SwitchyandWitchy [she/her]

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Joined 1 year ago
Cake day: December 18th, 2024
  • SwitchyandWitchy [she/her]@hexbear.netMtotraaaaaaannnnnnnnnns@hexbear.net•Capacitors -Trans Megathread from week 1/12/2026 to 1/18/2026English
    6·
    2 days ago

    do caps have frequency responses??

    They do! The frequency response of an ideal cap like @sodium_nitride@hexbear.net and @GiorgioBoymoder@hexbear.net describe is quite simple: infinite impedance at DC, dropping to low impedance at high frequencies. Specifically the formula is |Z| = 1/(2*pi*f*C) where |Z| is the magnitude of the impedance in ohms, f is the frequency in hertz, and C is capacitance in Farads.

    But real world caps have much more interesting frequency responses! A real non-ideal cap has both inductance and resistance as well. In general, capacitors will have a resonant frequency where their impedance is at a minimum, and above that frequency they behave like an inductor while below they behave like a capacitor:

    Depending on the type of capacitor, they they can also introduce significant levels of distortion to the signal since some behave non-linearly: their capacitance changes with the voltage of the signal. I think multi layer ceramic caps are notorious for this and are usually very undesirable to have in signal paths. And I think tantalum caps exhibit this as well, though less severely. Here is an example curve:

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