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Inductors behave like capacitors at high frequencies. This is of course due to the parasitic capacitance taking over.

Now, would it be possible to use an inductor as a capacitor for high-frequency applications? I mean, we can't put them in parallel with Vcc and GND, because this would simply be a short for the DC component, but is there no other configuration that might take advantage of the fact that they have parasitic capacitance?

Is there something I am missing regarding the behavior at HF? This sort of makes me think of how the diverging part of rocket nozzles actually increases the velocity of supersonic flow even more (against all intuition of the undergraduate engineer)...

For example, see the pictures below:

enter image description here enter image description here

And so, isn't there perhaps a way that one could take advantage of that parasitic part, and have a desired response with an offset, like so:

enter image description here

In which \$f_c\$ is the frequency at which (in this case) an inductor would serve better as a capacitor, than a capacitor?

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    \$\begingroup\$ Can? Well, it turns into a bad capacitor at high enough frequency. But a counter question would be what you expect to gain from it? \$\endgroup\$
    – winny
    Feb 15 at 13:52
  • \$\begingroup\$ Can you show us a specific inductor's datasheet which you intend/think of using it on such an hookup? I want you to be more specific of an application. \$\endgroup\$ Feb 15 at 14:02
  • \$\begingroup\$ I don't intend on using it for a specific application, but the question is more just for me (and perhaps others) to better understand the higher frequency domain. \$\endgroup\$
    – TheMAX135
    Feb 16 at 7:52

2 Answers 2

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You could say the same thing about a capacitor - at very high frequencies, the equivalent series resistance and inductance becomes significant enough to change the slope of an impedance plot.

But in either case, is the parasitic component going to overwhelm the characteristic component to the point of being a substitute for a designed component? IOW, is capacitive reactance going to become so much larger than the inductive reactance that you can use the inductor as a capacitor? Almost certainly not, and absolutely not for the vast majority of applications. IMnsHO

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  • \$\begingroup\$ Thanks for the description :), I think I may not have been too clear on what I meant. Please see the added graphics. I am specifically wondering about that high frequency as shown on the last picture, where the two intersect, and the parasitic takes over... \$\endgroup\$
    – TheMAX135
    Feb 16 at 8:04
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Very bad design practice. Parasitics are characteristics that manufacturers try to reduce, so you can only rely on the major characteristics which are well defined as part of the specification.

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