#84: Basics of Ferrite Beads: Filters, EMI Suppression, Parasitic oscillation suppression / Tutorial

This video discusses the basics of ferrite beads, and their uses for basic filtering applications. It discusses and demonstrates how ferrites act as resistors at high frequencies, and how this is used for EMI/RFI Suppression, improved power supply filtering, parasitic oscillation suppression, and others. The affect of the frequency dependent resistive characteristic of the ferrite beads is demonstrated by showing its effect on a swept RF signal, its effect on the rise/fall time of a digital signal, and its effectiveness of eliminating parasitic oscillation. Here are some links to the other videos mentioned in this video:
Harmonic content of square waves:
• #59: Basics of a Squar...
Analog Oscilloscope Bandwidth Considerations:
• #25: Analog Oscillosco...

[@softtransistor6729]

Thank you, you made me a better engineer than I was 10 minutes ago

[@SingTodayi]

Hello dear Sir. Could you please tell is it possible to check it with "multimeter"? If yes how?

[@Floyd..B]

​@@SingTodayi No, you need at least an oscilloscope. Multimeters are not precise enough and they don't go high enough in terms of frequency.

[@Afrotechmods]

I liked your practical oscillator example.

[@iforce2d]

I think I just learned more in ten minutes than a month of physics class.... and if I'm not mistaken you did this in one take as well. Excellent work!

[@sidejunk]

seconded. super useful video. i came across this vid because of a project that i'm working on, but it's gonna have to wait while i go through all of his other stuff.

[@abhaynatoo]

fourthed.[?].

[@Paul_VK3HN]

Fifth'd. Compelling demo. And as a result of watching it, I went straight to a homebrew receiver project with a Mosfet RF amp that was unstable above 7mhz. Added 2 turns thru a 43 bead, soldered it right on gate 1, and guess what? It worked!

[@CVEGeek]

I also concur.

[@boovaragan_sriram]

Sixthed, very good live explanation

[@JohnHill-qo3hb]

Your videos should be part of every theory lesson in schools and colleges. It is fine to explain it on a chalkboard but to actually see it on test equipment makes the theory sooo much readily understandable. I'm a visual learner as are many others, wish the internet and instructor/techs like you were around 40 odd years ago when I was desperately trying to learn this stuff...BRAVO ZULU

[@californiakayaker]

The bead on the base demonstration was almost magical. Great demo.

[@mitchellhw2006]

Excellent tutorial. You packed more useful info in a few minutes than hours of dry text from the library. Many thanks.

[@TheBdd4]

Thank you for another one of your excellent teaching moments. You are blessed with the ability to say just what needs to be said, no more, no less.

[@Radiowild]

I've used ferrites on occasion, but I never realized just how much loss they could create. There you go again teaching something I didn't know! :) Great Job! RW

[@Disillusioned_one]

Enjoying watching your videos, brings back memory's of being a TV engineer dealing with rf, if, pll, and singing ferrite beads in the line stages driving the customer dogs mad.

[@chuchan60]

Thanks again for your great videos! You are an excellent teacher and I for one very much appreciate you taking the time to make each one of your video lessons with such great demonstrations, examples, and experiments to help convey the concepts you are teaching!

[@zennsystems9433]

Excellent! Covered so much in a small Video... A must watch for all electronics related engineers. Thanks for a great refresher course.

[@robadoba8497]

Best ferrite bead video I've found! I'm an engineer trying to get up to speed to help solve a signal noise problem with equipment at work. Thanks for the great info!

[@garrickdedemeter3244]

Thank you for posting this excellent video! It has helped me to understand (on a QUALITATIVE basis) exactly how ferrite beads work. Though I am currently interested in filtering out barely-AUDIBLE-frequency noise (in the 10 KHz to 20 KHz range), I am now prepared to do some trial-and-error testing with different split ferrite beads, installed on both the power cord and audio signal cables of our A/V system. Thanks again!

[@ronaldwhittaker6327]

"thank you for this" its always better when an there's a coherent instructor explaining a thing for me sometimes the concepts don't leap off the page for me on top of the fact i don't speak electrical engineer so again thank you.

[@KL3NCH]

This is great. I loved the cross referencing to the 'scope. One area where it does get confusing is the use of various mixes dependent upon the application: use as a choke against use as a transformer. This leads to folks arguing at cross purposes on forums and elsewhere about which mix to use. A mix that works as an RF choke at a given frequency will most likely not be a suitable mix for a transformer at the same frequency for obvious reasons when you stop to think about it. I do enjoy your videos Sir.

[@katelikesrectangles]

The demonstration for suppressing a parasitic oscillation was brilliant!

[@das250250]

Your channel is high quality , very interesting channel , it is a must have channel for any electronics person / engineer . I wish i had more time to see all of them several times over .

[@j.t.johnston3048]

This is the best primer on ferrites I have ever seen. I really appreciate your videos.

[@sajadjolaeian5218]

I have used these ferrite beades before and i have known that they do sth by frequencies but i have not seen their waves on the oscilloscope,now i have beter veiw,how a great video was that🙏🙏🙏

[@danielpeters1754]

good info. I always wondered how effective those ferrite cores were and if they did anything. Thanks for clarifying!

[@kramsniggah4333]

This was the most informative and actually answered the questions I've had for years! Massive kudos w2aew!

[@DeltaXray444]

This is the best video I've seen on ferrites and how effective they can be.. excellent.

[@bobdehuisbaas1]

Other online sources only gave me some vague description of these mystery components but your demonstration made things very clear for me!

[@noname-gp6hk]

Thank you sir, this solves a few problems I've been fighting. You have an outstanding way of explaining things.

[@tunicana]

Alan, your videos are a must for everyone involved in electronic engineering. Thanks a lot

[@AppliedScience]

Great video!

[@BGLENN-dp4tx]

Excellent coverage. Hams (W2AEW) often have extensive, job related, knowledge and experience to share. I suspect that's the case here. Thanks, AA4BQ.

[@skilambi]

Great video...I always enjoy the way you explain things in such a simple manner...

[@lcradan24]

Excellent video Sir. You and thesignalpath are prob my favorite posters of educational info here. Thanks for sharing with us your knowledge, i look forward to more of your content.

[@jb3757]

This channel is GOLD MINE and the videos are Nuggets.

[@sayinpower3]

This video has earned yourself a subscriber sir. Very well done.

[@anicetdjada2025]

Nice video, straigh to the point ! More intuitive than hundred pages of unreadables applications notes... Nice Job;thank you

[@rihan-haque]

your 10 min videos are like summary of 1hour engineering class, but better and enjoyable.

[@The-Nil-By-Mouth]

I had an idea what those beads around transistor legs were for, but so good to see a demonstration. Thanks

[@1pcfred]

+Malcolm Hunter Was that like witchcraft, or what?

[@gerardoromano3436]

I know this vid is old, but gold ! clear demontrations, didn´t know osilators have oscilatotions on the base, I thought it only happened on tube circuits where the cheap and effective solution is a grid stopper resistor, most tubes where deigned for high frec. did´t know that bipolar transistor suffered the same issue. Now I know thanks to you! In fact 2N2222 is a high bandwith transistor (relative to say a BC548).

[@ronevans8404]

Good explanation, thank you. You sound like a good analog engineer.

[@danielg2716]

Thank you very much for your excellent explanations about ferrite beads. The clearest explanations! Thank you!

[@mgabrielle2343]

Indeed very well demonstrated, these filters and suppression of unwanted frequencies both within circuits and power supplies as these can directly affect other sensitive electronic equipment through power lines or other interconnections as well as radiate electromagnetic radiation as radio frequency interference, (RFI) so today you would not be able to market any product unless you meet all RFI regulation under the EMC rules, and only then you could place any product on the market and obtain a CE marking requirement.

[@dell177]

I worked as an engineering technician for a large op amp maker 45 years ago and we were always looking to increase the bandwidth of our opamps and multipliers. These were discreet devices that were about 1-1/2" square and had 7 to 9 pins on the base (I still have a few in my parts bins). The circuitry was on small printed circuit cards, these were put into a potting shell and then filled with epoxy. A cheap way to increase the bandwidth was to slide a small ferrite bead over the output pin -worked every time.

[@gurpreetbal1]

Very well explained Alan. I have a topic suggestion - back to basics video on filters. Something that shows multiple order passive/active filters and their performance. Thanks for making these wonderful videos.

[@pfarrell20]

Love the analog scopes mmmk, love the frequency response mmmk, superb content Mackey!

[@2lefThumbs]

Thanks👍 very well planned and executed run through of the basics (which is exactly what I needed)

[@mangeshmalgi279]

Thanks for the wonderful & practical explanation, of the usage of the Ferrite Beads.

[@computerlen]

Absolutely perfect presentation. So clearly explained and demonstrated.

[@MLFranklin]

Very helpful. Thank you! I'm planning on doing a CNC plasma later this year and the KZbin algorithm sent me here.

[@RaindropServicesNYC]

Fantastic video! Thank you very much for taking the time to post this video.

[@WaynJul]

I was right as my guess it was some kind of filter. I asked Best Buy and Office Depot and no one knew. Your explanation is very good. I am trying to find the same length power supply cord for my adventure cam without the ferrite bead on it. The cord came with a ten year old Cannon camera but works on my Ultra Pro X 10. The length is 18". My next step is to try Radio Shack for the cord I need. Subbed and liked.

[@ocdtechtalk]

LOL you asked Best Buy...You so funny.

[@TheCrazyInventor]

I always wondered how effective those filter beads were. Many products have those inside and I always ask myself "how much are these tiny ferrite beads going to help"... Thank you for showing us and making it clear! :)

[@The6Bird9]

I understand the principle of why it works... didn't realize it could have that magnitude of affect on at higher frequency. My question, how do you determine when you need to use this filter? What would be some symptoms? This question stemming from the fact that all of the computer related cables have them. AWESOME video!

[@iSolarSunrise]

You earned my subscription. Very basic but a good refresher!

[@oldasdihrt5993]

Really like these videos. What i like the most is the comments from guys that feel they have to mention that they themselves are engineers or graduates of M I T . The only thing that they engineer is a burger onto a bun at the golden arches for an 8 hour shift. Nevertheless....good video Thanks

[@movax20h]

Superb video. Very well prepared, I loved all the practical examples.

[@saintpine]

I needed a refreshing about ferrite beads, you've done and excellent job, thank you.

[@nickynorton]

Excellent presentation visuals are worth a thousand words ..

[@rjinnh3933]

Very, very well done vid with clear/concise info/presentation. Job well done Sir.......

[@acmefixer1]

I like your informative video. I never suspected that a simple PSO would break into oscillation at 200 MHz. I've built quite a few, but even if they did oscillate, my 20 MHz scope would never know it. Thanks.

[@marcisberzins]

I remember watching some weird twisted bits of sinusoid from homemade audio oscillator shown on my 5 MHz scope, now I got what those shapes mean.

[@josealexanderdeleonfernand7613]

Very good, you are very clear to explain, despite of my bad english you are a good teacher, thank you very much!!!

[@williammanganaro9070]

Truly informative. Well done. I understand much more about ferrite beads ! Thank You !

[@shadowwolf225]

... and you have another subscriber. Great video and thanks for showing demos on the 'scope. I've been looking for a good video on ferrites and I believe I found it.

[@noelguerrero2770]

As a former Instrumentation Technician, we usually get deliveries of industrial instruments with those things loosely bouncing inside the box. I usually pick it up and turn it this way and that not knowing what those darns are for. Now I know. Thanks.

[@valiza123]

I always thought that ferrite beads were electrically conductive. When I saw you put that bead directly on the lead I was sure a short was imminent:)). Thanks, opened my eyes and put ferrite beads on mosfet gates on my current project working at 300v, very clean switching right now. (Also added capacitors very close to the half bridge).

[@fredgarvin9262]

They are electrically conductive. Never put an inductor on a FET gate. That's the last thing a switching fet wants.

[@alexhoyos5343]

Fred Garvin you can’t just say never. applications may require to add a reactance to any location depending on its application. For example sometimes your biasing network may require inductors near the gate specially in radio frequency designs. Besides it is all relative to what your gate sees and its switching speed. You could put a a tiny inductor (fH) and if your frequencies are in KHz it simply won’t see it.

[@hla27b]

Just watched Dave's common mode noise video. Perfect timing :)

[@jonmcgrath3748]

Wow! I saw this link in the comments of a 3-part decoupling tutorial at allaboutcircuits, despite being a good article, your video explained more in 12 minutes than a month of reading online! I will definitely check out some of your other videos, I would love to see some more on choosing the correct part for different applications! (If you haven't already) Excellent video, and I'm shocked that this was done in one take - unless you have Hollywood level editing skills ;)

[@w2aew]

Yes, one take - after LOTS of prep, practice, and previous attempts....

[@laneboysrc]

A day where you learn something new is a good day. Thanks for making it a good day for me :-)

[@raymonda.koosha5824]

That was a great and informative explanations on Ferrite beads! Thank you

[@James_Bowie]

Excellent tutorial and demonstration. 👍👍👍

[@MantisRay861]

That's a really cool demonstration on ferrite beads

[@libratherm]

very useful information and nicely presented and explained. thank you Kamlesh Panchal - MD Libratherm

[@edinfific2576]

Great examples, the only thing I would add is side-by-side shots of before and after so that the results are even more obvious.

[@MrSte2222]

Really good video well explained I like the practicle demonstrations really help get to grips with the information

[@sdplusm3]

Thank you for this excellent 10 minutes (11:51 actually) of video that teaches a lot.

[@a000ab]

Very instructive video. Now I am thinking that maybe for the cases that the operational frequency of the circuit is in much lower ranges, it is even better to use bids made up of iron, instead of ferrite. Because if I know correctly, the "cutoff" frequency of iron is much less than ferrite. Though I have never seen any iron bids around a wire for noise cancelling ...

[@ronniepirtlejr2606]

Finally ,It all makes sense now! Thank you!👍

[@Ruben-oh4mj]

Cool...really enjoyed your explanation on this subject.

[@vaseemmehrancp9372]

Great .. The contents and Practical examples were good .

[@marf5303]

Great, very clear to understand and fun with examples.

[@tomvent1]

Great info!!! thank you !! I'm powering my gopro camera from a accessory outlet on my Harley Davidson and wondering if I would benefit in employing a bead on the usb power supply line to reduce any noise it might generate?

[@DavidGillooly]

Very nice video. Once again a super job in using instrumentation to explain and show the behavior. I wish the ARRL Handbook has such videos embedded in the pdf versions!! Dave, AA6RE

[@BrianHensleyRULES]

Great stuff, always learning something new from your channel!

[@chunkhutchinson]

Hi there, first of all let me thank you for your video, it has educated me to no end. I have a rfi problem I would like your advice with. I run a professional music studio and am always trying my best to cut down on noise. Recently I have had a dimmer switch installed on the studios lights. The dimmer switch is an old school MK type double switch not a new led one.. One dimmer for each rooms lighting circuit. I am using new Phillips led warm white bulbs which are great for my studios lighting bills and have been designed to work/dim with regular old dimmers. Indeed the Phillips led bulbs dim perfectly and smoothly, even better using the old mk dimmer than the Chinese led dimmer I had before. However, now it seems that with the dimmer installed I am picking up much more interference in the room while recording. The classic one is a single coil pickup in a guitar. It goes crazy with interference when the lights are on and then shuts up when I turn the lights off. Same with guitar amplifiers. Of course I know that guitar pickups and tube amps always pickup interference anyway it's just that the audible volume of said interference has got much louder since I fitted the dimmer. Please is there any way I can choke/suppress or isolate the dimmer switch in order to reduce the noise/interference without having to sacrifice the dimmer and go back to the standard on full of off switch? Perhaps ferrite beads on the connections to the dimmer? Or do I have to spend a lump on a 1:1 isolating transformer and completely isolate the lighting circuit from the rest of the power in the studio. Any help would be much appreciated. Thank you.

[@w2aew]

It is possible that these snap-on ferrite cores might help - installed in the wiring box for the dimmer or light fixture, or both. But there are no guarantees. It may help to understand which device is the major contributor. If the dimmer is replaced with a switch using your Phillips LED bulb, is the noise lower? Or, if regular incandescent bulbs are used with the dimmer, how is the noise? Some of the manufacturers have written information on reducing noise/interference: www.lutron.com/TechnicalDocumentLibrary/360484.pdf

[@LeonAllanDavis]

Good information. Very helpful. I have a wireless mic set up and at times I get very bad RFI. I suspect it's a cell phone of one of my neighbors. The cord from my lapel mic to the transmitter acts like an antenna and picks up the very high frequency of the phone. I ordered some ferrite beads off Ebay. Hope that solves the problem...

[@tatonilo]

Hi, thanks a lota for many & many hours on your channel, for sure i will spend in the next future. great way to explain this things. see you soon. D

[@henryrobinson9837]

man your good,hope your still into it

[@samvoelkel2046]

Excellent demonstration. Thanks.

[@jasonbrent]

Thank you. I've got an older DC voltage standard I've been trying to repair. It has 4 "VN66AK or 2N6660" transistors, 2 of which have berrylia washers on them... after watching your video I'm guessing those washers act as EMI filters on the high speed VMOS transistors.

[@antonmoric1469]

Excellent vid on ferrite beads, enjoyed it.

[@dancollins1012]

Thanks, really appreciate this video, there's very little out there on ferrites. Would be great if you could follow up with an 'ferrites applied for power input conditioning' video - examples of successfully addressing spikes from noisy power supply lines, at voltages like 5V and 24V. The small number of youtube vids on ferrites and tvs diodes are pretty theoretical/high level and don't demonstrate how to perform component selection

[@30YearOldBunta]

Trying to diagnose weird wiring on my old Nissan and I am considering adding ferrite cores on some of the finicky sensor wires. I've added some to the LED retrofit headlights and I actually think it made a difference in drivability. I have a feeling the fans on the heatsink was creating enough RF and maybe that combined with no isolated ECU grounds it might be enough to distort a 5v cam signal, which I have had issues with in the past.

[@irawarnaca8133]

Great Video! Thank you for all your hard work.

[@nicolaecampan2385]

Excellent! Helped me with an erratic CNC router! Liked and subscribed! :)

[@1959Berre]

Once again a very instructive video. Thank you.

[@jonh2119]

Thank you for this, gave me lots of ideas to try! 👍

[@ocayaro]

You reminded me why I subscribed two years ago.

[@AerialPhotogGuy]

I really appreciate your very informative tutorial videos! I'm learning a lot from you! Thanks again! :-)

[@577buttfan]

So awesome seeing this man!!

[@andrewmullen5770]

You are awesome, Thanks so much for taking the time to explain this stuff! -Subscribed

[@1903A3shooter]

Great as always, wonder what the freq. was in that burst? Looked kind of sinister and a real trouble maker but easy to fix. Glad to learn something new as always. Dave.

[@Debraj1978]

Thanks for a practical demo, I always wanted to see. My idea is that supply decoupling and EMI suppression are 2 different use cases of ferrite bead. 1. Supply decoupling = ferrite bead in series and acts attenuates high frequency noise to pass through, hence decoupling. 2. EMI suppression = ferrite bead as a transformer (not in series), basically provides a low impedance for high frequency noise, so that they do not radiate through parasitic antennas. Or, is 1. and 2. same???

[@Ogma3bandcamp]

Excellent! Another lesson well learned. Thank you.

[@paulfrischknecht3999]

awesome explanation and examples!