Capacitor resonance frequency tool - Page 1
Forum section: electronics / beginners

author: kumar
author_rank: Contributor
timestamp: April 02, 2015, 12:21:40 pm
content: I am looking for a free software which will show the capacitor resonance frequency in graphics after entering the RLC values ( for a single capacitor as well as parallel capacitors of different values) Please share if you have one or post a link to download.

author: Simon
author_rank: Unknown
timestamp: April 02, 2015, 12:23:00 pm
content: surely this is something that the manufacturer of each capacitor should provide.

author: kumar
author_rank: Contributor
timestamp: April 02, 2015, 12:33:54 pm
content: I can not find a software on these sites. Can you please post a direct link to download?

author: Simon
author_rank: Unknown
timestamp: April 02, 2015, 12:37:16 pm
content: the manufacturer should be providing a graph in the datasheet of the capacity IF they have done the tests.

author: Zero999
author_rank: Super Contributor
timestamp: April 02, 2015, 12:40:10 pm
content: I'd suspect that not all capacitors will have sharp resonances. If the dielectric losses are very high at the point when XL= XCthen it will be overdamped so no resonance will occur.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: April 02, 2015, 12:40:40 pm
content: LTspice?

author: KJDS
author_rank: Super Contributor
timestamp: April 02, 2015, 01:05:12 pm
content: If you want it free, then just put the equations into an open office spreadsheet.

author: Stonent
author_rank: Super Contributor
timestamp: April 02, 2015, 01:36:14 pm
content: Surely wolframalpha can do this. If you know the formula then it definitely can.

author: Stonent
author_rank: Super Contributor
timestamp: April 02, 2015, 01:42:20 pm
content: http://www.wolframalpha.com/examples/ElectricCircuits.htmlhttp://www.wolframalpha.com/input/?i=RLC+circuit+10ohm%2C+12H%2C+400uF&lk=310R, 12H, 400uF, 60Hz.

author: Zero999
author_rank: Super Contributor
timestamp: April 02, 2015, 02:24:19 pm
content: https://www.yuden.co.jp/productdata/navigator/en/002/E-TechNote_090219.pdfhttp://www.kyocera.co.jp/prdct/electro/pdf/technical/esreslti.pdfhttp://www.electro.fisica.unlp.edu.ar/temas/Notas_de_aplicacion/Capacitores.pdf

author: free_electron
author_rank: Super Contributor
timestamp: April 02, 2015, 02:28:50 pm
content: tdk, murata and other cap manufacturers all have that software readily available.i have posted the links on the forum before.

author: KJDS
author_rank: Super Contributor
timestamp: April 02, 2015, 02:30:27 pm
content: Whilst it's handy to have online references and manufactures details, it's well worth working through the maths at least once as it brings a better understanding of how circuits work.

author: TimFox
author_rank: Super Contributor
timestamp: April 02, 2015, 02:46:29 pm
content: The OP was looking for a calculation app. Some of these answers were about the self-resonance characteristics of capacitors (usually referring to the series combination of Cs, Ls, and Rs) that should be specified (at least graphically) by the manufacturer. A useful specification format is to show the self-resonant frequency as a function of capacitance for a manufacturing series (e.g., 1206 C0G 100 V). ATC gives thorough specifications on their RF capacitors, e.g.:http://www.atceramics.com/product_specifications.aspx?id=40#rfperformancebut I could not find their specification for the parallel-resonant frequency (above the series-resonant frequency shown in the link) online. It was given in their hard-copy catalogs when last I looked.

author: Marco
author_rank: Super Contributor
timestamp: April 02, 2015, 04:57:07 pm
content: Quote from: TimFox on April 02, 2015, 02:46:29 pmIt's useful in certain circumstances, for something like decoupling the SRF is misleading metric though ... as Ivor Cattvery combatively points out. (A higher value 1206 capacitor will generally be better than a smaller value 1206 for decoupling ... the SRF might be smaller but if at any given frequency the impedance is smaller or equal the SRF is irrelevant for choosing between them.)

author: TimFox
author_rank: Super Contributor
timestamp: April 02, 2015, 05:09:32 pm
content: One reason to pay attention the (series-mode) SRF is that the capacitor is inductive above that frequency. That can cause interesting interactions with other devices connected to it.Many years ago, we had a simple JFET circuit at 64 MHz where the source was bypassed to ground and fed from a resistor from a negative supply to determine the current. (There were multiple FETs, each with a switch in series with its source resistor.) The drains were inductively coupled to a transimpedance amplifier. We had a 100 nF X7R in parallel with a 1 nF C0G for each source bypass.Testing the complete amplifier showed exactly the wrong response, with a dip at 64 MHz. With the switch off, the gain was much lower but showed a peak at 64 MHz. Due to bad karma, the 100 nF capacitor was inductive at 64 MHz, and parallel-resonated with the 1 nF at 64 MHz. (These capacitor values are from memory.) Replacing the source bypass with a properly chosen intermediate value (below its SRF) was the easy solution. With only the large capacitor (above its SRF), the frequency response would show the inductive reactance in series with 1/gm of the FET.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 03, 2015, 02:44:03 am
content: ^ So what you're saying is, someone actually *believed* the lie that "small caps in parallel with big = good"?Power supplies are impedance networks, just like any other. They are generally intended for much lower impedances, but their structures nonetheless resemble transmission lines, and therefore posses characteristic impedance, resonances and cutoff frequencies.Best design is had, not by piling disparate caps together and praying that they work, but by careful design, taking into account the body length, trace length, via length and so on between capacitors, component pins, and the surrounding circuit.Most often, a bulk capacitor is desirable, for no other reason than its ESR. Certainly not for energy storage, or minimal impedance. This is the biggest benefit to tantalum capacitors: the ESR is well controlled, and stable against temperature change, so the power supply network's frequency response can likewise be designed for stable performance.Tim

author: TimFox
author_rank: Super Contributor
timestamp: April 03, 2015, 01:30:36 pm
content: Yes, that was a "learning moment" early in my career.Note that using the larger capacitor by itself (above its SRF) was not the lesson learned.Instead, I measured the candidates myself on a good -hp- analyzer to choose caps for the next iteration of the prototype.