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# Simulating Inductor SRF using Lumped Elements

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#### chiques

##### Full Member level 3
I see that the equation to determine SRF of a capacitor or inductor is:

But when I follow this simulated circuit shown on https://www.microwaves101.com/encyclopedias/self-resonant-frequency , the equation is the following for an inductor.

I see they mentioned they added a factor of 1000 so the equation works out. What I don’t understand is why the equation is way off from the SRF version.

Note: The Microwaves simulation in my simulator is close but still off. I get 1.7GHz SRF where they get 2.3GHz.

When I try to correct the simulation to

I get:

Anyone have any idea what I’m missing here?

Are you assuming that any RF inductor has a parallel capacitance of 1 pF? It's just a typical value used in the microwaves article. Has to be replaced by an actual value for your inductor. Also ESR may be different.

I think it's just a typo: in the article (of microwave101) they wrote pi*2 instead of pi^2 and SRF*2 instead of SRF^2. The factor 1000 is used only to convert between measurement units.

### noori.re

Points: 2
I don't know from where are the 1.7GHz and 2.3GHz results.
51nH in parallel to 0.2pF resonates on 1.576GHz.

I think it's just a typo: in the article (of microwave101) they wrote pi*2 instead of pi^2 and SRF*2 instead of SRF^2. The factor 1000 is used only to convert between measurement units.
This is confusing because if I correct their typo's, the circuit does not simulate :/

"Does not simulate" means?

"Does not simulate" means?
The simulation does not resonate at the desired frequency.

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