# Simulating Inductor SRF using Lumped Elements

#### chiques

##### Full Member level 2 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?

#### FvM

##### Super Moderator
Staff member 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.

• chiques

#### albbg 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 and chiques

### noori.re

Points: 2

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

#### chiques

##### Full Member level 2 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 :/ #### FvM

##### Super Moderator
Staff member "Does not simulate" means?

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