#56: Basics of Capacitor & Inductor self-resonance, parasitics, etc. - Tutorial

This video builds upon the last two videos:
Current and Voltage in Ls and Cs: • #54: Back to Basics Tu...
LC Resonant Circuits: • #55: Back to Basics: T...
that discussed the voltage and current properties of capacitors and inductors, then discussed the concept of resonance. This video looks at some of the practical aspects of component selection by discussing the various parasitic properties of real-world (non-ideal) components, and how these properties can dramatically alter the device behavior. The concept of self-resonance and its consequences is shown (and measured using a dip meter). The point of the video is to show that the proper choice and selection of capacitors and inductors can be surprisingly complex, and that increased study is needed if components are going to be operated at or above their self resonant frequency.
Show Notes: www.qsl.net/w2aew/youtube/Para...

[@Ne3M1]

10 years later and still one of the best LC tutorials out there. Thank you for sharing your knowledge and experience.

[@Seiskid]

9 years later and I'm reading up on which LC combination to use. Not getting very far online, but I knew that you would have done a tutorial on this topic. Sure enough here it is. Super helpful. Super clear. If you ever see this comment thanks so much.

[@reverse_engineered]

This is amazing. I graduated from a 4 year electrical engineering degree program at a major university and I had never once been exposed to the idea of self-resonance within a component like that. I knew parasitics existed, and I knew a bit about the mechanisms that caused them, but we had never stopped to look at the practical implications of those parasitics, nor ever looked at what typical values for those parasitics might be. Thank you for providing such wonderful explanations. I am going through your entire series of videos to see what else I have missed!

[@dave-d]

Me too! Alan is the man.

[@DumbledoreMcCracken]

KZbin is becoming The University. Just need a curriculum and a bunch of syllabi to create the learning framework.

[@yurigagarin4974]

nobodys perfect 😁

[@MsFrisker]

My

[@michveldvvid]

@QueHubo Parcero oh my gosh it's like you could get a PhD here on KZbin

[@alocin110]

Hello Sir, there are two things I would like to mention regarding this educational tutorial on the topic: 1. Your voice and accent are so perfect, gifted, being a teacher or commentator, very soothing, well controlled, and very relaxing. 2. I wish if every school has teachers like you to clearly explain a principle of operation. Although the video is only 20 minutes but you covered the topic which probably needs more than an hour. I watched every second of your video without blinking an eye. You should be teaching in MIT or Berkeley. I liked your video and going to subscribe to your channel. Thank you Sir.

[@fabrizioricciarelli]

I'm a teacher too, in IT Sciences, and I cam say that this guy has a natural attitude, a gift from the nature. Bravo and thank you very much for your time.

[@W1RMD]

Excellent! 27 years a ham and never did I understand it this way. I especially enjoy how you tie in the schematics with the real world components and use multiple pieces of test equipment to show how it works. Thanks!

[@micropyro7470]

Great presentation. Been a ham and electronics enthusiast for over 45 years. Came across this video in my research for tesla coils and the subject of discussion is very pertinent in the construction of tesla coils.

[@KhawjaAziz]

Appreciate your well structured tutorials and attention to details.. I am a old timer and worked on analog Op Amp with my mentor (late) Bob Pease.. Keep up your great work and please save your hand written notes for publication it would be an asset as an accompanying workbook or lab manual. I am rekindling my Analog interest and setting up my home lab to keep my brain cells active during my post retirement life. Kudos !

[@w2aew]

Amazing that your mentor was Bob Pease! Such a sad week when we lost Bob and Jim Williams - two giants in the analog community. i always loved Bob's "What's All This _____ Stuff Anyway?" column in Electronic Design. I had the pleasure of meeting Bob once during a seminar tour. Thank you for your nice comments and happy to hear that you're enjoying my videos.

[@gotoluc]

Excellent information and presentation Thanks for taking the time to make this video Luc

[@davideisenberger6197]

Thank you very for taking your time to make this video! You are an "Excellent" Instructor, precise and quite easy to follow. 73's David K8KEM

[@Wil_Bloodworth]

I need to watch this video about 37 more times. Thanks Alan!

[@nlimchua]

Another good one, Alan. I've watched many instructional vids done by others for topics you post, but yours are by far the BEST (not to mention the clear vocal presentation)! Keep 'em coming!

[@myenjoyablehobbies]

That was very very good explanation on parasitics, I have a better understanding of modeling components, as well as working with frequency dependant circuits now, even transistors have parasitic capacitance at higher frequencies. This video is a great tutorial on why certain values of capacitors are used at rf rather than just throw a large capacitor for rf filtering and such. Thanks for taking the time to put this video together.

[@dallasjohnson6060]

thank you for this, doing some modeling and incorporating parasitics...very helpful!

[@sobakete]

Fascinating video. As clearly explained as it can get. Thanks a lot!

[@myenjoyablehobbies]

That was extremely helpful. Thank you for taking the time to explain this in very good detail.

[@3D6Space]

Thank you so much! Wonderful video! I was going to make one about this, but you did a much better job than I could have done! Awesome!!! -t

[@marcelopires1267]

Thank you a billion for this inspiring video! I wish I had this much concise information during my Electrical Engineering graduation! This will be very useful. You got another subscriber!

[@microdrone]

I've been eating up your videos, well explained, and give me access to many important concepts, Thanks!

[@w2aew]

Thank you - I'm glad you're enjoying them. Not sure if you are aware, but I do keep an index file (arranged numerically and by topic) online to make it easy to search for a given topic/video: www.dorkage.com/youtube/W2AEW_video_index.pdf

[@microdrone]

Cool, I just downloaded it, thanks for the great resource. Especially important given my roots in microcontrollers and ( way back ) COMS style digital circuits. Now very interested in analog circuit design, this type of depth is highly appreciated! Perhaps I'll get finally my technician class amateur license after all... :)

[@iamhe999]

Very well done.... Kudos.... as an instructor, you are well worth following...

[@321reh]

One of the BEST VIDEOS you have put out!! Thanks!!!

[@surendersingal2192]

Great demo of self resonance testing meter n thus giving a tool to designer to see what range ideal components actually operate? Thankbyou

[@gearhead1302]

Lol wow I'm just learning this stuff and I thought it was all coming together but there is wayyy more details than I thought haha. So much to learn. This guy must really know his electronics.

[@TheCrazyInventor]

I've said it before, but I'll say it once again... You maken some really good videos! Excellent examples which really gave me a good feel for the parasitic properties of components.

[@seamusdemora5598]

Excellent! Hearing your explanations, and seeing your equations reminds me that all of these things which I used to think about frequently - are still true. :)

[@Plutonion2]

Arguably Your best video yet .

[@AfternoonPlay]

Alan, this really great. Thank you for sharing your knowledge. Greg.

[@ReasonForemost]

@w2aew Your tutorials are excellent, very informative and helpful. You do a great job of preparing your notes, drawings and test equipment which sets up an environment that is very conducive to learning. Your knowledge and very impressive teaching ability are the best contributing factors, great voice too. Just found you, I've subscribed and looking forward to more of your outstanding videos. Thank you very much, your exceptional technical knowledge and efforts are very much appreciated.

[@keithostertag]

Thanks again for a great video. I think you are one of KZbins most under-rated secrets. One of these days you will be getting thousands of views, not just a few hundred. Do datasheets for caps and inductors list the self-resonant frequency? Or maybe some other parameters related to their practical frequency limit (or frequency dependent losses)?

[@AxelWerner]

EXCELENT TOPIC! EXCELENT Explanations! Things clear up A LOT with your lesson here. It also tought me a valuable lesson on how to determine what parts can be used for and/or why not! especialy if you try to build some sort of oscilator this becomes VERY HANDY! THANKS THANKS THANKS A LOT!! and PLEASE keep up this EXCELENT work!! This is the type and quality of knowledge that to me is realy hard to find on the nets freely. and for some reason i didnt had much luck with books yet.

[@Pwaak]

Informative and important "journey" about electronic components! Thank You!

[@tarcrocksalways]

Great video! :D Nice to understand almost every thing just during the first watch. Thanks

[@celtichongy]

Brilliant, thanks for sharing great information to us all.

[@gradimirpejic9085]

ABSOLUTELY BRILLIANT, Regards from Serbia

[@cny02253]

You hit a home run with this video. Had this video been available when I was back in school, it would have saved me a couple of weeks trying to figure out how what I was studying fit into the bigger picture. Yeah, I finally got it but this would have been a superb practical introduction. Do you plan on covering stuff like Thevenin, Kirchoff, and other analysis aids at some point in the future?

[@opablo_gm]

Incredibly clear and educative video !!! Idea for another video: Your interpretation of a basic rig schematics. The simplest mono-band CW transceiver that you can find. (You can google Splinter QRPp for an example). It would also be extremely educative to hear you read an schematic like this... what you spot; what you identify; how you group the components in your head and how you understand based on the configuration and values of the components how each of the pieces would behave.

[@InsanePlanter]

great video definitely lifting the veil im designing a metal detector and needed a clear concise explanation for the coil frequency.

[@ChrisWilson5006]

Very clear, I see now why circuit modelling software can be so expensive, it's akin to aero modelling software for race cars *SO* many variables! Thanks Alan.

[@N2RRAny]

@w2aew - love watching your vids. This vid helped me a lot on a couple levels. Explains why certain projects didn't work as I expected due to a couple variables I didn't take into account. Back to the drawing board. Thanks!

[@tradegrabber4854]

Great tutorial. Thanks!

[@snowboarder50000]

Great work bro, thank you for the break down

[@kmmankad]

Eagerly awaiting that video. :)

[@hubercats]

Fabulous video!

[@JoshuaMorganUSA]

Okay, that makes sense. Thanks for the informative reply!

[@n2mpm]

Excellent Video

[@xrayrep]

I've found a lot of YT videos that explain how an LC tank circuit works, but until I found THIS one, I didn't have a clue about how to select the best L and C values for a particular frequency range. In other words, is a large L and a small C better than a small L and a large C? Well, now I know that it depends on many factors that have to do with the makeup of the individual inductor and capacitor. Thanks so much, W2AEW for this very informative tutorial!

[@BHR477]

I like ur voice, kept me concentrated ,,,, grate Video 😊

[@tribulationcoming]

I have reached a point in experimentation that I will have to do some calculations involving tanks. Tanks for these explanations. Qualitative "Gut Science" has reached it's limits, Qualitative evaluation has to take over. From what is going on to why and how.

[@ysvsny7]

Brilliant 👏thank you for clear explanation

[@keithking1985]

that was brilliant.. love the HeathKit tester.. : )

[@raymondragodon8048]

Thanks love it keep up the good work

[@Avionics1958]

Thanks a bunch ! ok now I am going to build the modulation stage and try to understand how it works. because I learnt it is a common base after watching your new video I can see the input and out put of the CB but R4 is supplying the bias voltage to this base so the base is not sitting at "Zero" is this because it needs to keep the T2 on to make the path to 0volt to keep the tank going?

[@fredtaylor1915]

I never understood f dependent R until this vid. You need to switch to an electronic whiteboard for your examples. Thanks, KI5QZW. ps Man, you scratch the surface and it gets really complicated fast. Every little bit help me understand Ham theroy.

[@w2aew]

Any suggestions for electronic white boards?

[@TSulemanW]

Nice explaination

[@Avionics1958]

wow what a beautiful answer you are great.

[@MrMac5150]

You are the best dude.. Thanks

[@sneakyboii732]

thanks a lot for this tutorial! you have no idea how great it is to find someone who explains the practical aspects of electronics well, especially since i'm in college, with many things in the labs which i don't understand i can always come here to find an explanation. Also, how does the impedance spike for the inductor at the resonant frequency? If the impedance of both the inductor and capacitor is equal, shouldn't the equivalent impedance be half of the impedance at resonant frequencies?

[@w2aew]

It's because, unlike resistors, there is a phase shift between the voltage and current in a capacitor and in an inductor. These currents will constructively or destructively combine depending on whether the LC is in series or parallel. See my video #55 on LC resonant circuits.

[@uiticus]

Greetings sir did you ever make a video discussing how to build a servo circuit to control the speed of a motor?

[@Avionics1958]

Thanks Alan for your videos. a question: If I want to design a simple RC (series) filter can I say that the RC circuit at resonant point has "Zero" impedance and hence at that particular frequency i.e resonant frequency the circuit will be a short circuit and hence the voltage is zero hence its filtered out? appreciate if you respond. cheers

[@electronicatutorial]

Can you use a network analyzer in smith chart format to calculate the operating frecuency of inductor and capacitors?

[@justinmckibben4534]

Nice video!

[@cyclinginuk7969]

hello, I started following your videos about inductors and capacitors parasitic effect. The video is really helpful for me. It is possible to get some video on how to design the equivalent circuit of an inductor simulated in hfss. I am trying to get an equivalent circuit of my antenna but I don't know which kind of model I have to choose and a basic value of inductor and capacitors. If you could do this, then it will be helpful for me. Thank you for providing this kind of videos.

[@w2aew]

I"ve never used HFSS, so really can't provide any info/advice regarding modeling in this tool.

[@JoshuaMorganUSA]

Thanks again for a great video! You are a wonderful teacher. Question: because of the opposite nature of the components above a certain frequency, is it ever done that in high frequency circuits, you actually use an inductor as a capacitor, and vice versa?

[@Avionics1958]

Hi Alan I was checking this a three stage FM TX and they talk of a feed back capacitor BUt I don't see any feed back and I did some readings and found out that the internal capacitance of collector base and base emitter of the transistor acts as the feed back in very high frequencies is this correct? sorry to keep bothering you.

[@stefflus08]

Nicely explained as usual, although I had to come back to it. I remember seeing it several years ago. I find it amazing that we get any high freq stuff done at all, especially into the GHz. It is always talked about to keep traces short and such, but signals have to travel fairly long conductors with very significant L and C, there's no way around that. So I'm guessing there are tricks to isolate resonances, perhaps it's a bit of a tuning juggling game of different sections? I suppose when I design one of my hobbyist circuits my signals degrade in shape and quality through the stages because I lack control of these parasitics, and perhaps the trick of HF is to recondition it in stages? Or do you keep it from degrading all the way?

[@w2aew]

There is a lot of careful design considerations and component selections, along with careful layout needed for successful RF/microwave designs to work.

[@RohitShindes]

What happens if I swap l and c for eachother at high freq in ckt. Will I get a min impedance at high freq if I use inductor in place of actual cap in ckt. Will their boths function change vastly?

[@w2aew]

***** Ideally, yes. the impedance of an inductor increases as the frequency increases, which is just the opposite of a capacitor where the impedance decreases as the frequency increases. Of course, once the frequency is above the self resonant frequency then things tend to somewhat reverse due to the parasitics. However, it is highly unwise to design a circuit to *depend* on the behavior above self-resonance, because it is non-ideal, not specified, and not well controlled.

[@RohitShindes]

Okay. Thankyou. Liked your videos. ☺😊😊

[@JosiahRitchie]

+Rohit Shinde Thanks for asking that. I was wondering the same thing, if one could find L and C with the same resonant frequency and have them counteract each other making for a wider frequency range by essentially causing L and C to switch places. Seems like finding the right components to perfectly match each other's dips could get really tedious, but an interesting thought exercise.

[@1903A3shooter]

Great, love the uncircumcised cap. W4GSM

[@maurosobreira8695]

Thanks a lot Allan, excellent Video as usual, and straight to the point. One question I have relates to the high Z / 50Ohms choice that I have on the AWG...Will the choice of High Z compensate for not using the 10db Attenuator?

[@w2aew]

No. The high-Z / 50ohm selection only tells the generator what load to expect so that the voltage reading on the generator is correct. The output impedance of the generator is always 50 ohms in both cases. You might want to watch this video: kzbin.info/www/bejne/qnTPdmupa7eNmsk

[@maurosobreira8695]

Thanks Alan, It's clear. I just noticed that this question was in the wrong video. I watched #56 then jumped to #100 (where the question is relevant), but watched from different device (my mobile phone probably). when I went to the desktop to type the question I had #56 in my mind. My bad!

[@Avionics1958]

Wow thank you I didn't even know there is a current probe. so if I want to use my ordinary probe then I just connect the crocodile on one side of the resistor and the probe head to the other side of the resistor in order to see the current?

[@Avionics1958]

Hi Alan, if I have a tank circuit in a FM transmitter and lets say the tank resonate at 108 MHZ from the FM circuits I can see a transistor is driving the tank circuit. can you explain to me 1- is this transistor acting as amplifier or a chopper to provide AC to the tank? 2- At what frequency this transistor should operate in order to keep the resonance going. 3- some times I see a capacitor across this transistor what is the purpose of this capacitor? appreciate if you answer these.

[@mnoxman]

When I went to Vo-Tech back in the mid 80s we were taught self resonance. Selection is also based on the Q value (as you mentioned) and the EIA standard values. Having 9 digits of precision in your calculations is great but when you calculate out 3.54663194903K but the nearest values are 3.3 or 3.6K +/-5% and now you dip your foot in to Monte Carlo simulation pool. Trivial using modern computers but reserved for 'high end' in the 80s. So then it became an engineering argument of do you use "common" 5% resistors or more expensive (at the time) 1% precision resistors?

[@tonyperry6702]

Alan, in an old AM radio does the antenna and the tuning capacitor form a tank circuit? If so, is it typically a series or parallel circuit? Any help you can provide is appreciated.

[@w2aew]

It is typically a parallel tank circuit - the antenna loop is in parallel to the capacitor(s), so that it presents the highest impedance at the resonant (tuned) frequency, thus having the highest voltage response to RF at the tuned frequency.

[@eie_for_you]

Many antenna traps use the self-resonant frequency of an inductor to eliminate the need for a parallel capacitor to create the parallel resonant circuit needed for a trap. I have yet to find a means of determining how to calculate the required inductor build characteristics to do this. It seems that it is a trial and error process (?), but I have a hard time believing there isn't some sort of formula that can be used to at least get you in the ballpark.

[@sarasteven80]

Thanks. great video. Just a question. The impedance of a capacitor at low frequency should be a hyperbolic function and is not linear or am I missing sth ?

[@w2aew]

+nima dabidian I guess I should've mentioned - both axis are log scales...

[@sarasteven80]

I see. That makes sense

[@electronicatutorial]

If the interior of capacitors like in the plates the and the inductors turns is made of superconductors would it that reduce dramaticaly the parasitics inside?

[@solemansk6204]

excellent ,,thank you sir

[@hyperboogie]

As always - great video. A question regarding the the skin effect. Since a bigger cross section of a wire equals lower resistance, is it fair to say that the skin effect results in higher resistance of the wire as well?? Also, if the current passes through the outer layer and not through the center, why not use tubes instead of wires?

[@diamony123]

Is it safe to say we are basically talking about waves 180 degrees out of phase is resonant frequency cancelation.

[@risack8640]

Very informative. I have no problem solving the inductance of the inductor as I understand it , I need to use L= 1/2#^2xf^2 x C , right ?

[@w2aew]

Yes, the formula is shown clearly at 1:50 in the video

[@wesleyxu8849]

How about make a video about band-gap reference?

[@das250250]

Can the dip res freq in the real world capacitor or inductor not be used in circuit as the " res freq " in a tuned circuit requiring the same resonance ? That is , with no inductor or capacitor needed.

[@w2aew]

It could - but it could likely be very unpredictable due to manufacturing tolerances, etc. as well as sensitivity to different mounting configurations and variations, since we're dealing with parasitic inductance which is not specified, and is highly dependent on lead length, mounting configuration, and physical orientation.

[@guywhoreallylovesempiretod5906]

I dont understand a single thing you’re saying or how I ended up here but greetings from a traveller amongst the internet

[@TheHarpanOnly]

Very kind of yoy

[@electronicatutorial]

With the advent of superconductors it is going to be much easier to design any circuit or at least less parasitics. If it can be implemented in real practice, what do you think?

[@Avionics1958]

I Alan one more question. How do you measure current with an oscilloscope?

[@nemanjatodorovic2803]

How did you know that this capacitor has 85nh when you counted resonance? Whether it be in this way to make a LC meter? Excellent video! Thanks!!!

[@tonyperry6702]

Alan, I'm new to electronics and I'm beginning to work on old radios. I had thought that when a tuning circuit went into resonance current was peaking strong. Is this the case?

[@w2aew]

It depends on the circuit. A parallel resonant circuit looks like an open at resonance, while a series resonant circuit looks like a short.

[@mumtazshamsee5029]

Superb!

[@grzesiek1x]

can you recommend any nice books about all this staff you are talking about? Especially about design on the transmitter/receiver circuits (it is for learning porpose so less ICs involved it is better). I try to build simple and very low power transmitters / recievers to control different devices at home (like rc car, light and other small things). But I have noticed that I can't really learn from youtube (because all videos scratch only the surface but I need a lot of more details how it works etc.)

[@w2aew]

I like practical books like "The Art of Electronics" by Horowitz & Hill.

[@Avionics1958]

Thank you for highlighting the RC I dont know why I put RC.

[@craxd1]

Stray inductance and capacitance are the nightmare of a homebrewer, especially when designing large amplifiers. That was also why the large manufacturers that produced them had problems as well, where they added neutralizing circuits with "gimmicks." What looks good on paper does not necessarily work well after layout and construction, as parasitics can bite you in the behind. A grid dip meter is a lifesaver in building RF circuits, and especially in building RF amplifiers.

[@Mike500912]

As an aside, this would suggest that at frequencies above resonance, an inductor could be used as a capacitor, and vice versa ? Would that be a practical use of C and L ?

[@w2aew]

In theory, yes - but in practice, no. The parasitic inductance of a capacitor and the parasitic capacitance of an inductor are *not* specified or predictable.

[@Avionics1958]

Thanks Alan, I wished I could send you the circuit diagram of this simple three stage FM TX as I can not see the feed back or what they refer to I don't understand. if you can not its ok I understand as you must be very busy.

[@JohnRaschedian]

Thank you!

[@BEdmonson85]

Just curious; are there any application(s) you know of where these parasitic properties are used to an advantage in a circuit? Where it would be desirable?

[@w2aew]

There might be - but it would not be very common, since parasitics are not well controlled and can vary wildly from device to device, as well as with physical mounting configurations.

[@crocellian2972]

BEdmonson85 - Any FPGA. Was that a real question or an EEVBlog troll?

[@ydonl]

Electric guitar pickups turn this into a mysterious art form.

[@wk2w]

Would you consider discussing the electrical-mechanical system analogy (LCR - spring, mass, friction)? I know it's not really relevant to your other videos, but your perspective might be helpful.

[@w2aew]

Interesting thought - I'll think about it.

[@ydonl]

@@w2aew I, too, think this would be pretty terrific! Eye-opening. I don't how it flies around your wheelhouse, though. Not bein' pushy. :)

[@surgingcircuits6955]

I've not been able to find the notes: www.dorkage.com/youtube/Parasi... Are they still available? Thx.

[@AcousticBruce]

Is there ever an application to use a capacitor or an inductor above its resonant frequency?

[@scootndute579]

If impedance of an inductor starts to drop after it's resonant frequency is reached (and your supplying a very large frequency) does that mean there is no more oscillating magnetic field produced by the coil?

[@w2aew]

There is still a field, it just means that the inductor is beginning to be bypassed by the parasitic capacitance.

[@sanakana5564]

Thank you for the explanation ^_^

[@eljardinero8752]

At 7:19 in the video you mention that the plates of a capacitor can have some inductive effect. My understanding is that ceramic capacitors are much less inductive than electrolytic capacitors. I've noticed that ceramic capacitors can have the same capacitance value but have different physical size. Does the physical size of the capacitor (more specifically the plates) have any bearing on the inductive effect of the capacitor?

[@w2aew]

There are a factors that affect the parasitic inductance of a capacitor. Physical size, number of plates, physical shape/design of the plate and terminations, etc.

[@eljardinero8752]

Thank you.

[@eljardinero8752]

Is the inductance of the capacitor directly or inversely proportional to the plate size? I'd like to have a dip meter and a frequency counter. Is that somthing you can buy in a store?

[@w2aew]

The plate inductance is a function plate size and configuration. Long thin plates have more inductance than short wide plates.

[@w2aew]

Frequency counters are common, easy to find from test equipment vendors and distributors or online. Grid dip meters are a bit more rare. Still available new from MFJ Enterprises or buy used on eBay, etc.