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

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

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

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

I liked your practical oscillator example.

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!

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

Great video!

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!

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

The demonstration for suppressing a parasitic oscillation was brilliant!

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

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

"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.

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.

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! :)

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.

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

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

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!

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

Absolutely perfect presentation. So clearly explained and demonstrated.

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!

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

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.

1) I'm really enjoying your videos 2) What is your profession? Does it involve teaching, because you deliver the material really well 3) Ever though of elmering?

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

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.

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.

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

Great .. The contents and Practical examples were good .

You reminded me why I subscribed two years ago.

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

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.

Nice clear demonstration. Kind Regards. . . Andy

It is the common mode (versus differential) signals that are attenuated by the bead on the USB cable. Common mode signals cause the entire USB peripheral to act like a monopole antenna.

... 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.

Yes this is a terrific reference; EXACTLY what I was looking for.

man i wish i had all your knowledge

Very well done and answered a lot of questions

Great Video! Thank you for all your hard work.

Thank you for sharing your knowledge. I was reading through the manual for a new video camera I had bought, and it mentioned this thing I'd never encountered before, that snaps around the power supply cable. Of course my curiosity was piqued, so I had to find out more. Thanks to your video, it all makes perfect sense: suppression of high frequency electromagnetic radiation, by encouraging lossy inductance. My questions is: is this to protect the camera itself or is it just bundled in to comply with regulations to prevent other devices from picking up interference? Is the operation of the camera likely to be affected if I don't bother putting it on? The cord is supposed to be wrapped around the bead (in parallel) so that the cord passes through the middle part twice. The design of the supplied bead is such that it is a very tight fit and I am concerned that I will damage the insulation of the cord if I were to clamp it shut. If I simply left it off, what's the worst that could happen? (I would be filming on battery power 99% of the time anyway. Very seldom using the power cord while filming. Only there for charging the batteries.) Thanks again for the clear explanation.

Great stuff, always learning something new from your channel!

GR8T introduction to the "magical beads". I really never gave them much thought. After see cause & effect, I'm a believer. Also your video quite well done. I couldn't have gotten a better view if I was standing their (no, not a stalker:)... SuBsCriBed. Thank you. Cheers

Always wondered why I saw transistors with beads on the legs.

WOW....WHAT A GREAT PRESENTATION....IM A FAN...TY!

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

Bravo Romeo Alfa Victor Oscar !

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.

awesome explanation and examples!

Thank you! This was comprehensive and quick :)

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

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!

Great Content, Thank You.

Very useful information, thanks for sharing.

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).

Nice but you left out an impotent issue of the difference between ferrite beads used for common mode filtering like on USB cables and those used for differential mode filtering, like in your examples.

I really enjoyed this. really good intro for me

Have you ever thought of taking over the world ? ,:) another top video from theMaster !!

excellent explanation.

Excellent video. Thank you very much.

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🙏🙏🙏

Great explanation, thanks

Great video, learned something new

Great explanation.

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

Excellent video! Now I need a good source for these ferrite beads...

I gain another good information from you sir,,thank you,,fantastic video :).

I just order some Ferrite beads one for my headset and one for my laptop cord.. thank you

Good video, you are a great speaker!

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

I am only speculating but I think the high frequency content is filtered out because this energy is converted to heat in the ferromagnetic material. Since the input signal is is alternating this causes the dipoles to change their polarity and this dipole movement causes friction -> heat in the ferromagnetic material. Can someone back up my speculations :P ?

If we consider a switched power-supply that runs around the 50-100 KHz range, what would be most (cost-)effective and simplest to filter any parasitic signals from the hashing oscillator on the DC output? Beads ? Capacitor grounding (low-pass)? A pi-filter ? An RF trap ? I guess some switching power-supplies use a kind of active filtering as well, but I would categorize that as rather expensive and more complex. Would you have any thoughts/comments on this and what would you advise? Thanks a lot for considering my question. I found your video very instructive and entertaining.

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

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).

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 .

Thanks for the clear explanation !

Excellent presentation visuals are worth a thousand words ..

Very good introduction. What about energy loss in bead? How much can it dissipate?

Thank you you saved me a very expensive oil truck data cable tear down

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 ...

So Ferrite beads create an implosive centripetal effect/motion down the wire, like how a magnetron works in a microwave, through suction as all magnetic fields rotate. Thus never displaying high frequency EMI as it's not traveling along the outside of the wire (centrifugally). It's Schauberger 101 ! Here's a picture showing this in motion. simplylivingwater.com/wp-content/uploads/2014/04/Schau-pipie-cross-sec.jpg

Will a ferrite bead disrupt the data traffic on a cat 6 data cable running from a switch to a phone or PC? We are getting what we think is EMI interrupting phone calls. I need a way to filter it, but not kill the needed data traffic on the cable. Great video and explanation.

Serious question - are you able to clone yourself and send your clone over to Australia? If I had you as my electronics teacher, my understanding of this topic and all other semiconductor related topics, would be at a far higher level.

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

another great video! just one question though. you explained and showed how the ferrite bead blocked parasitic oscillations at the base of BJT. i can see how the ferrite bead's inductance can filter high freq. noise at that point, but you also mention you have added a series resistor before to achieve the same goal. i dont understand how adding a resistor can filter the high freq. components. is that something to do with RC circuit coupled to it? thanks

Hi! And for a field-effect transistor? For MOSFET? If it is in a switching power supply, which output (gate, source, drain) is best to wear a ferrite tube?

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

Very useful on ferrite bead applications...can you please upload a video on how to use Vector network analyzer with different model of testing like smith chart, polarized, vswr?

Great video. Many thanks!

I'd be really interested to see an explanation of the cause of the parasitic oscillation on the base. How come there is no trace of it on the collector as well ?

Thank you. Very informative video!

Great upload thank you! 😊

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.

O.K. let's get down to the true grit here & make up some experiments with some toroid cores. Explain the differences and how wire wound cores help RF... especially all that ratio stuff we hear about with baluns & UN UNs.

The AC cord plug into the back of an a piece of equipment, inside before the power supply there is a silver square box that filters out RFI/EMI from the AC outlet. Is there ferrites beads inside this RFI/EMI box or what kind of filters are inside these RFI EMI filters for the AC outlets. EE engineers have told me these AC RFI/EMI filters cause a lot of current leakage issues i'm guessing from the AC hot wire to the earth ground. I have tried opening up these silver box RFI/EMI filters but looks like filter cavities or something.

I am curious if the scope was set for 50 ohm input impedance, or the nominal high impedance during the ferrite bead tests? It would seem to require 50 ohm input on the scope to get the voltage division associated with the filter, but maybe this is wrong...

Any suggestions on eliminating noise from a BLDC cooling fan in RF circuits? I have read and observed that this noise emanates from the fan's ground wire. The only solution I've found that really works is to use a seperate power supply for the fan, that is a seperate ground reference. The question is, can I create a truly isolated supply for the fan if it is using the same AC wall outlet voltage source as the RF circuit? I haven't figured out how to do this yet. Any suggestions would be appreciated. Thanks always.

congratulations! You have a new subscriber

Great video. Have you ever seen an assortment pack of beads? Can't seem to find any.

Thanks for the lesson sir… if i use emi ferite bead at end of grounding wire in motorcycle or car engine, is that can improve eletrical circulation and can get better performance?