Questions about About Self Resonance Frequency (SRF)

[hari_preetha]

Sir,
I am confused in getting reading the values of frequency vs Self resonant frequency (SRF). For example, if we take Johanson capacitor capacitance Vs Frequency graphs. Suppose if we take R14/0603 case style in the screen shot below, frequency of values 1.3 GHz to nearer to 24 GHz and capacitance values from 0.2 pF to 100pF.

I have the following queries

(1) Case style 0603 is valid for , which frequency range and which capacitor values.

(2) more than 100pF(more than 101pf, 102pf,103pf......) and below 0.2 pF( below 0.1pf, 0.09pf,0.08pf.... etc), what about the values of frequency and SRF, is it valid.

(3) Case style 0603,how we have to read exactly SRF and Frequency.

(4) For case style 0603, what are the SRF values are valid and what are the frequencies valid.

 

[THINKER_KAM_MAN]

just a suggestion.

SRF = 1/(2pi x (sqroot (LC)),

and at SRF voltage across the cap could be high due to Q of circuit.
so avoid using values that resonates at your frequency of interest

 

[volker@muehlhaus]

(3) Case style 0603,how we have to read exactly SRF and Frequency.

1. Choose your C value where you want to find the SRF.
2. Find that value on the x axis
3. From that point on the x axis, draw a vertical line.
4. Find the intersection of your vertical line with the blue curve (blue for 0603 size, as show in the legend)
5. From that intersection, draw a horizontal line to the left y axis.
6. See where your horizontal lines hits the y axis. This is your SRF value.

 

[hari_preetha]

1. Choose your C value where you want to find the SRF.
2. Find that value on the x axis
3. From that point on the x axis, draw a vertical line.
4. Find the intersection of your vertical line with the blue curve (blue for 0603 size, as show in the legend)
5. From that intersection, draw a horizontal line to the left y axis.
6. See where your horizontal lines hits the y axis. This is your SRF value.

Sir,
As you said, I did. Johason Company capacitor SRF at 25pF(0805 case style) is 2GHz, SRF at 30pF(0603 Case Style) is 2GHz.
For 2GHz at 40pF, no case style of Johason company capacitors are suitable.
For 2GHz at 40pF, no case style of Murata GQM series is not suitable.
For 2GHz at 40pF, no case style of AVX company is not suitable.
If a single capacitor value is suitable for single frequency, what we have to do remaining frequencies.
As I said above example 40pF at 2GHz , no case styles in any company capacitors are not matching. In this case what we have to do,which company case style we have to choose for 40pF at 2GHz.

 

[volker@muehlhaus]

As you said, I did. Johason Company capacitor SRF at 25pF(0805 case style) is 2GHz, SRF at 30pF(0603 Case Style) is 2GHz.

Correct.

For 2GHz at 40pF, no case style of Johason company capacitors are suitable.
For 2GHz at 40pF, no case style of Murata GQM series is not suitable.
For 2GHz at 40pF, no case style of AVX company is not suitable.

If you need 40pF with SRF at 2GHZ (or above), now you have a problem, if these components do not exist. This is something you need to check during circuit design. Now, you need to re-design your circuit to work with components that do exist.

 

[hari_preetha]

If you need 40pF with SRF at 2GHZ (or above), now you have a problem, if these components do not exist. This is something you need to check during circuit design. Now, you need to re-design your circuit to work with components that do exist.

Sir,
For example, we can take 39pF at 2GHz, market available vendor component of capacitor value of 39pF different companies with different case styles are available.
In the vendor company different case styles and different companies are available at 39pF. As we discussed earlier 39pF at 2GHz, AVX,Murata GQM Series, and Johanson no case styles are suitable.
In this case 39pF at 2GHz, what we have to do, which company and which case style we have to choose. 39pF capacitor is existing in the Market, but we are in confusion with choosing case style and company.
Can you clear it
You can see Vendor Component link at 39pFhttps://in.element14.com/jsp/search/browse.jsp?N=2103+202460+110110464&Ntk=gensearch&Ntt=capacitors&Ntx=mode+matchallpartial&No=0&getResults=true&appliedparametrics=true&locale=en_IN&divisionLocale=en_IN&catalogId=&skipManufacturer=false&skipParametricAttributeId=&prevNValues=2103+202460&mm=1000002||,&filtersHidden=false&appliedHidden=false&autoApply=false&originalQueryURL=%2Fjsp%2Fsearch%2Fbrowse.jsp%3FN%3D2103%2B202460%26Ntk%3Dgensearch%26Ntt%3Dcapacitors%26Ntx%3Dmode%2Bmatchallpartial%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_IN%26divisionLocale%3Den_IN%26catalogId%3D%26skipManufacturer%3Dfalse%26skipParametricAttributeId%3D%26prevNValues%3D2103%2B202460

 

[volker@muehlhaus]

In this case 39pF at 2GHz, what we have to do

1) You need to understand what SRF=2GHz means. The 39pF capacitor has 39pF only a low frequency, much below SRF. You can use the capacitor at SRF to block DC, but the effective capacitance at 2GHz is not 39pF.

2) It is possible that you will not find any 39pF capacitor with >2GHz SRF. Checking available components is part of the design process, during the design phase.