Parasitic Inductance of Cadence Capacitor Varies Very Little with Its Size

[Elecemperor]

Why Parasitic Inductance of Cadence Capacitor Varies Very Little with Its Size

After dealing quite a lot with the parasitics of inductors and capacitors, I'm wondering why the parasitic inductance of a capacitor seems almost independent of its size? I'm simulating rfmimcap capacitors in cadence, ranging from 20f to 900f, and their ESL seems to change only from 24p to 34p. Why?

 

[D.A.(Tony)Stewart]

Re: Why Parasitic Inductance of Cadence Capacitor Varies Very Little with Its Size

capacitance is the related to size of gap and area between conductors, whereas ESL is attributed to the conductor lengths.

 

[aaron_do]

From "RF Circuit Design Theory and Applications" by Reinhold Luwig and Pavel Bretchko (section 2.6 in my 2000 edition), Inductance of a parallel-plate line = Miu*height/width (H/m). So for a square-shaped MIM capacitor, the parasitic inductance is independent of the length (you could give it an inductance per square if you like). Ideally, you would only see the inductance of the line feeding the capacitor, but the actual inductance will depend on how nicely your MIM fits the parallel-plate model.


regards,
Aaron