Talk:Ferrite bead

Insufficient content
I have no time now to improve it and I wonder why nobody cares. Neonil 13:52, 23 April 2007 (UTC) IMO ferrite beads is one of the most significant discoveries in electronics in recent 20 years but still nobody can tell anything except high end analog or power supply gurus. Do I really have to write this article? Neonil 13:55, 23 April 2007 (UTC)
 * I don't know about the discovery of these being in the last 20 years, but they have only become greatly necessary recently, as generally circuits below 4mhz don't need them as much. Higher frequency circuits need them a lot more.  Also, note that the picture here is not technically a "bead" -- it is too big.  I've seen ferite beads and cores used in two ways:

(I've moved the list of related articles into the article.) Maybe someone else can expand on these and add them to this article, or merge this article with some of the above links. --ssd 14:58, 12 August 2007 (UTC)
 * 1) Beads on small wires intended to carry DC input or output will block high frequency RF noise from traveling past the bead.  Typically, low frequency and DC lines coming off of high frequency circuits use beads like this.
 * 2) Large beads and ferrite cores on coax cables prevent high frequency RF signals from using the shield of the coax as an antenna, allowing only balanced signals between the shield and center conductor to flow.  (See also balun.)  This is what is in the picture.  (Note: when I first typed this, the picture was clearly a balun.  Now it is a better picture that could be considered a large bead that is also a balun.)

Disagree with merging this topic.windsun
 * I've removed the merge request. This isn't the same as a balun. --ssd 04:35, 26 August 2007 (UTC)

There is a better article for this technology
After doing some research, I see that this article is pretty much unnecessary and is better described in the much better article Magnetic core. I'm turning this into a redirect and will salvage anything useful from here to put into that article. DMahalko (talk) 00:15, 23 March 2009 (UTC)
 * You are ABSOLUTELY wrong. :) But if nobody cares I will too. Ferrite beads are NOT inductors, not cores, not pods, not rods, not chokes, not everything else; they are devices especially designed to use resistive impedance at high frequencies for noise suppression. I don't want to be offensive, but what you're doing demonstrate your absolute ignorance in the subject. Cheers, Neonil (talk) 16:06, 15 April 2009 (UTC)
 * It is clear from the edit history that this started as "your" article, so of course you have returned to "defend" the article you WP:OWN. The fact that you state that this is not a choke shows that you don't understand the purpose at all, because that's exactly what this is. It passes some frequencies but blocks others, which is what tuned inductors do. DMahalko (talk) 00:50, 17 April 2009 (UTC)
 * By saying things like "pass frequencies" or "block frequencies" you demonstrate falling out the topic again, which is sad but not fatal :). I can help you understand: Inductor and bead both "block high frequencies", but bead dissipates high frequency energy, while inductor (ideal one) does not. And the second thing: I don't own this article, but nobody permitted deletion of article in Wikipedia, except for reasons listed in WP:DP. I wait for people to improve this article, add content to it, not to delete it! There are facts not clearly known regarding ferrite beads (resistive property degradation due to bias current) and there are things completely unknown (good mathematical theory), so I expected some expert to disclose them here one day. Neonil (talk) 12:46, 5 May 2009 (UTC) P.S. DMahalko, add content if you can! Add it! I cannot, too damn busy now :( Neonil (talk) 09:35, 7 May 2009 (UTC)
 * I found this while browsing Random Articles and read it because I'm an electrical engineer. The article seems to be aimed at people who wonder 'what the bumps are in electrical cables', but got off to a bad start by claiming that a ferrite bead is an inductor. A ferrite bead has the effect of increasing the inductance of the cable, but it's not the inductor. Pavium (talk) 06:37, 27 June 2009 (UTC)

this article should not be redirected to magnetic core. they have a different composition and totally different applications.

The article conflates Ferrite Beads and Ferrite cores. The two are quite different. eg the pix in the sidebar saying that the chokes are wound on ferrite beads is nonsense. Those things are ferrite CORES. A ferrite bead is quite specific, it's something you slip over a wire. — Preceding unsigned comment added by 119.18.11.19 (talk) 23:06, 22 February 2016 (UTC)

"Magnetic core memory" does not belong to this article
There is no connection; the only common thing is ferrite, and, maybe, "bead" appearance, while principles of operation and purpose are absolutely different. Neonil (talk) 13:01, 4 February 2011 (UTC)

General comments and changes I made
I see it's been a while since any activity here...(just looked @ the revisions...Lots of recent activity on the article, but little talk...)

I agree pretty much with --ssd. In the picture, while the classical small bead has a single hole, the right hand ferrite is indeed commonly referred to as a bead most certainly due to its close association to the single hole versions, though it is officially called a multi aperture core, but with the wires is called a wound bead, or supressor. The left hand choke may not have a ferrite core, depending on its manufacture.

---not so. A coil wound on a multi-aperture core is often an Inductor, eg is not intended for EMI suppression ---. — Preceding unsigned comment added by 119.18.11.19 (talk) 23:10, 22 February 2016 (UTC)

While the “returning of energy at a later time” and “back-emf” are fundamental characteristics of an inductor, these do not provide a good flow of understanding and are not views that are relevant in this explanation. It is the characteristic of reactance and its use to cause attenuation of varying signals that is relevant. It is the reactance that is important in this area of filtering. The loss component info is added later and also significant, but not always desired.

RE --ssd item number 2: Perhaps a fine point, but beads used on low or high speed cables, such as modem or monitor cables, to remove common mode signals that may either be radiated or picked up, are not commonly called baluns. The term balun is normally used in the context of RF transmission lines and then a more accepted term is “choke balun”. I made no corrections on this point.

Due to the fact that these are so often seen on cables these days, I think a short article specificly on them is ok...  Noted, that is is still here...

RE: Neonil's comments and some further comments from --sdd. Ferrite can be used for "cores" and that is a very common way of referring to them in the industry. Calling a "bead" a "core" will hardly end the universe. I also changed the text BEACUSE ferrites are NOT always used for their resistive loss component. This is common yes, but it is not necessarily desired in all uses. It is common to use them below resonance where there is significant reactance, yet the resisticve component is near zero. The ferrite loss component starts to dominate at and above resonance.

36+ years @ Motorola desiging with ferrites.

Forgot to mention that I kept the reference as it was in that section, but did not seek it out to see how it explained things. I comment based on experience designing with many types of "beads"..

Perhaps a good reference to add it this one: http://audiosystemsgroup.com/RFI-Ham.pdf

I stopped by here as a result of Googling for some manuf data after making some measurement on some clamp-on beads I had. Wiki came up in the hits, so I just wondered what it said and couldn't resist improving things. It’s been a while since I edited on Wiki. I hope I haven’t erred. -- Steve -- (talk) 02:07, 26 November 2012 (UTC)

Comments and questions
1. This reactance is commonly referred to simply as impedance, although impedance can be any combination of resistance and reactance.

Actually, impedance is by definition the combination of resistance and reactance.

2. "A ferrite core or bead can be added to an inductor to improve, in two ways, its ability to block unwanted high frequency noise. First, the ferrite concentrates the magnetic field, increases inductance and therefore reactance, which impedes or ‘filters out’ the noise."

Is the sentence implying that a bead is added in series with an inductor?

3 "Second, if the ferrite is so designed, it can produce an additional loss in the form of resistance in the ferrite itself."

What is the meaning or implied idea of "so designed"? The sentencen is ambiguous or I don't understand how there can be an additional loss in the form of resistance. The loss can be in terms of heat or signal level but not in terms of resistance.

4. I can't quite visualize how a snap-on bead over a wire produces a filter (LC I assume). An equivalent circuit and a simple schematic would be helpful.

ICE77 (talk) 20:28, 13 October 2015 (UTC)


 * Regarding #4, a ferrite bead on a cable is literally part of an LC low-pass filter. The wire passing through the toroidal ferrite forms a 1-turn series inductor.  That's the L.  The wire is connected to a device that has some capacitive load; that's the C. 149.117.9.27 (talk) 19:30, 1 June 2018 (UTC)
 * It may seem strange that a part snapped on the outside of a wire with no connected conductors can change a circuit. The reason this works is because this is not a DC circuit, but an AC circuit, and part of the circuit is in the magnetic domain. --ssd (talk) 20:32, 1 March 2020 (UTC)

Explain why the signal isn't blocked
We need a paragraph on how a ferrite can block high-frequency interference but not high-frequency signals. Eg. using it on a USB cable does NOT block the transfer of the USB signals, even though they can reach ~ 1 GHz. This is because any common-mode differential signal (e.g. USB's LVDS = low-voltage differential signalling) has exactly the same current flow in anti-phase down the cable on parallel cores: so the ferrite has no effect on them. — Preceding unsigned comment added by 82.10.237.122 (talk) 15:41, 8 November 2015 (UTC)

I really am having a hard time understanding: 1. The difference between RF noise and electrical noise, and 2. How a ferrite core can stop one but not the other? chevyorange 05:38, 29 February 2020 (UTC) — Preceding unsigned comment added by Chevyorange (talk • contribs)


 * There probably isn't much of a difference between RF noise and electrical noise, except that RF noise is at radio frequencies and can both radiate into and out of the wire, and electrical noise is in the wire. Either can cause the other.  The chances of RF escaping the wire increase as the length of the wire approaches 1/4 wavelength, where it can become a good antenna.  I'll proof read the article shortly and see if this can be clarified. --ssd (talk)

Inductor Energy Dissipation
In the overview section, there is a statement: "A pure inductor does not dissipate energy". That is not true; Consider some mining equipement. Or even a home PC (on which you edit this article) with ATX power supply. Launch some resource-intensive process, like mining (gathering something like bitcoin or ethereum). Or rather a video movie encoding process. Take a dynamic microphone (one with a high-ohm large-diameter coil inside), connect it to preamplifier (like one, in your mixer line in). You will hear a process, even if you move a couple of meter away from mining equipement. As you come closer, you will notice, that greatest power transfer to your ears would occur, when you will align the coil winding with the yellow-black wires (+12V line, that usually comes to your CPU/GPU/ASIC, into typical 8 pin molex connectors). +5V line would "sign" alot, when you move your mouse, or press a keys on usb keyboard. And most dissipation occurs at PSU swithing frequency, which is out of audible range(typically 65-80 khz), and can be measured with oscilloscope, or recorded to line in of your audio card (with use of capacitor). So that statement is not true. Inductor DOES dissipates energy! Even at audible frequencies. Even straight wire. Period. Please, correct the article..
 * Actually, that statement is correct, a pure inductor, by definition, can't dissipate energy. The catch is, the examples you give are practical inductors, not pure inductors.  (Pure inductors are theoretical and can't be built.) --ssd (talk) 20:35, 1 March 2020 (UTC)