#204

[@JackZimmermann]

When I started with electronics, I said to myself that I would never work with RF. You, Sir have changed my mind with all your excellent videos. I keep going back to watch videos for ideas. Thanks a bunch!

[@szaszafaja]

That is exactly what happened to me when I bumped into this channel. One of the best content creators on yt.

[@VoidHalo]

Yup, same. This channel got me much more interested in RF.

[@aduedc]

Thanks for great clip. Tunnel diodes are quantum mechanical devices. The electrons tunnels through the barrier as the barrier become too thin, instead of going over it. Just like science fiction movies, that people and things go through wall. The tunneling speed is much faster than speed of light, and is almost infinity. So, it is fun to investigate it. To get a clean oscillation, you need to measure the negative R of tunnel diode and cancel it with almost the same amount of positive resistance. So, putting a low resistance pot and adjusting it to get a clean oscillation. Of course, I would put diode and tank and the pot all in parallel, instead of series as you have it here. Also, it might be a good idea to have a DC block capacitance between tunnel diode and the pot and tank. As you know, to get a microwave oscillation, you replace your C & L of the tank with pieces transmission line that intersect your main transmission line in a point like a bow tie or use some sort of resonant cavity. Also Tunnel diodes are very expensive and people use NPN transistors ( like 2n2222) backward ( ie. emitter to positive and collector to negative ) to get the similar effect. In this configuration as the depletion region in the base increases as a result of emitter to base biasing the base region gets smaller and smaller until the carriers can tunnel through the barriers. The reason for backward use of NPN transistors is that emitter region is doped much higher than the base region and therefore by backward biasing it almost all of the depletion region will extend in the base region and decrease the effective base thickness. Other negative resistance devices, such as IMPATT and GUNN Diodes, are fun to play with.

[@user-tq8gs3oe6b]

Another excellent tutorial on this interesting topic. A big thank you for your passion and commitment. A friendly greeting from sunny Italy. Nello

[@helioshaul3924]

That was the best instruction I have witnessed to date.

[@christophernetherton9389]

Fully agree!

[@SuperFredAZ]

I have worked in RF engineering over 50 years designing varactor tuned rf front ends for television receivers. We heard about tunnel diodes in the 60s, but no one ever came up up with a good, cost-effective use for them.

[@w2aew]

The only place I’d seen them used is in the trigger circuits on old Tek scopes

[@docaliquot4189]

Thanks for a great trip down memory lane, Alan! As a budding ham and EE back in the late 60's, Dr. Esaki's little wunderkind fascinated me. Actually built several gizmos around the GE 1N2939....a 100 kHz. crystal calibrator, 2 M foxhunt transmitter, and a Heathkit Tunnel Dip Oscillator (which still sits on my shop shelf, working to this day!).Often thought what a great electronic countermeasures device a tunnel diode would be, with it's harmonic-rich output coupled to a broadband, high power GaNi amplifier. ;>)

[@uploadJ]

Wow. American Semi wants US 99 each for the 1N2939 TD today.

[@hubercats]

Another excellent tutorial. I especially appreciate seeing how you use simple instrumentation to perform basic device characterization (I.e., tracing the I vs. V curve). Thanks very much for making and sharing this tutorial.

[@DavePKW]

Alan, I sure am glad I discovered your treasure trove of videos. You do such a wonderful job. Thank you.

[@Radiowild]

Great video! Funny thing is, there is a question about tunnel diodes in the current "extra" exam question pool. Never really given them much thought due to their applications. I never really given them much thought. You did an excellent job showing just how they react.

[@11zekim]

Great tutorial Alan, and my favorite "lost art" subject, too. Thanks! Maybe worth noting that these magical things are no longer made, so parts like your test subject are rare and possibly quite expensive. These days the best way to experiment is to source old-stock Russian tunnel diodes on eBay.

[@uploadJ]

Well, a company named American Microsemiconductor seems to be in the business of making tunnel diodes, although they are a bit pricey ... but if one TD gets a piece of test equipment operational again, one hundred US$ might be worth it!

[@kd5ozy]

Have not thought about those in a while. Refreshing!

[@omsingharjit]

Whenever you Explain Doing Things practical it's Awesome to watch That what you just Teach Before .

[@ldandco]

Finally an explanation of Tunnel Diodes in actual (good) English that is understandable. Yours should be the first option to come out when doing a search for Tunnel Diodes on youtube. Unfortunately it is not.

[@w2aew]

+ldandco I suppose the more thumbs-up and views it gets, the higher it will appear on Google...

[@PapasDino]

Great video as usual Alan, amazing how little I know until you explain stuff! 73 - Dino KL0S

[@VoidHalo]

I'd be really interested in seeing you do a video on lambda diodes.

[@pramodsinghyadav7580]

amazing man !!!! I got to know a lot about tunnel diode and that to in a practical way.

[@RandyUpchurch]

Excellent presentation. Thanks for taking the time to demonstrate how the tunnel diode works along with some applications. Randy, N4NOM

[@w2aew]

Randy Upchurch Thank you, and you're welcome. I hope you enjoy my other videos too.

[@1903A3shooter]

THAT thing should be called a goofy junction.

[@DAVET38]

Another great video Alan. Thanks for such a clear explanation.

[@Cyrob-org]

Clear and simple as always, thanks

[@MichaelLloyd]

I really enjoyed this video. The tunnel diode is a lot more interesting than I would have thought.

[@ingussilins6330]

Similar curve can get from P channel and N channel field effect transistors ( lamda diode ).

[@annaplojharova1400]

The tunnel diode speed is indeed practically limited onl by the circuit parasitics, but the speed of regular (I mean NPN or so; you still need a hf type) modern transistors is so the real life limitation is also just in the parasitics, so bottom line about the same. That means you can make a negative resistance using a pair of such high frequency transistors (and their bias source) and you end up with very similar performance. On top of that, unlike the real tunnel diode, the key parameters of the transistor pair based negative resistance (mainly the slope and the peak/valley flip currents) are extremely well predictable and controllable (you just need to know the bias current and the temperature, literally nothing else), so consequently these become way more predictable and stable in a real circuit. That is the reason why tunnel diodes are a thing of the past for vast majority of the applications. And because transistors are easy to integrate, the transistor pair negative resistance is a structure is used practically everywhere in modern radio and many analog circuits (oscillators, Q-boosters for on chip LC resonator tanks, synchronous clocked comparators in AD converters, gain boosters in low power opamps and comparators,...)

[@robertcalkjr.8325]

Nice job Alan. Thanks.

[@BMRStudio]

Again a nice video! Thx a lot! Paper and pencil always the best:) I think this diode also good for peak detection with sample and hold circuit.

[@despiertagab]

IIRC, tunnel diode reverse current is quadratic, not like a little resistor. That's used for RMS measurement with backwards diodes. Great tutorial!

[@cny02253]

Outstanding Alan! Especially the links. (I have 500 and 400 series Tek scopes!) I had thought of suggesting this topic, then thought -"nah, too niche" -LOL!

[@VoidHalo]

I used to wonder why they don't use tunnel diodes in microwave applications. But I guess they don't really operate at a very high power, especially compared to a cavity magnetron, do they? This channel's great. It's been getting me more into RF stuff. Thanks for taking the time and effort to make these. Cheers.

[@Luzt.]

Superb! If YT had been available in the 70's and 80's you would have been a star, Sir! (and I used to say 3rd conditional is of no practical use ;-)

[@BryanByTheSea]

Excellent and informative as usual. Keep them coming.

[@knkp513]

This is the second of your video's I've seen and I am really excited I found them. Thanks for doing this!

[@w2aew]

Stephen Copeland I'm glad you like the two that you've found. Only 203 more to go to finish up the channel!

[@JosephBatten]

***** Finish the channel???? But whhhhhhhhhhhyyyyyyyyyy ??????

[@Loscha]

John Batten I think he meant that there are 202 of his other videos for you to catch up

[@CH_Pechiar]

Superb as usual. I could be useful if you write on the notes used during the video the episode number so as to have a quick reference between the document and the video. Maybe in the filename or maybe just handwritten on the papers. Thanks as usual. CH!

[@mrjohhhnnnyyy5797]

Great video, plenty information, but not too much for one take. Thanks to You, now I know what that tunnel diode exactly doing in my scope. :)

[@OlegMazurov]

Tunnel diodes are awesome. There is plenty of Russian ones still available, they are good but the current is low.

[@yoramstein]

Low current can be amplified. Life is not easy.

[@thomasdial8664]

Google or duck duck go can be your friend: tunnel diode amplifier, tunnel diode oscillator. I have one somewhere, and this makes me want to dig it out and experiment a bit with it. Thanks.

[@silvergmc]

Excellent video! I always learn a lot, keep up the great work!

[@AmanNidhi]

thanks for the tutorial !! enjoy all your videos

[@user-rk7td4cj2p]

Благодарю за сюжет.Вопрос-а снять характеристику на осциллографе получится?

[@eeramzi]

Great video as always, I never understand it until now. Many thanks.

[@vhm14u2c]

I have not encountered one of them yet, AFAIK, but I’m ok with that. Since I didn’t know they existed, if I didn’t have a schematic, I would have questioned the validity of the diode, but your explanation gave a new outlook in case I came across one of those.

[@w2aew]

Not a very common device, especially these days, but certainly unique.

[@scarpaz]

Great video, great explanation. Thanks for making it.

[@warunakumara7671]

teach us how to calculate the biasing resistor values to bias it in the negative resistor region and act as a oscillator

[@eidahmed26]

very nice work ..... thank you very much you make understanding of rtd very simple is the diode you used in the experiment has a data sheet

[@lidarman2]

With resources like you, there is no excuse for EE students not to excel in school. Well done.

[@cekpi7]

Unless you are lazy

[@jacobrandall4891]

thanks dude! Really well taught. As a low frequency power guy, I think these RF diodes are crazy interesting. I was thinking of ways to treat the diode as a variable attenuator. If you push more DC bias through the diode, does the RF insertion loss decrease?

[@w2aew]

Actually, what you're describing is really an application for PIN diodes, not tunnel diodes. Check out my video on PIN diodes...

[@nityanandadas5575]

Excellent. Really enjoy this. Is there any way to visualize the I V curve of tunnel diode in Scope ?

[@mikeleo9463]

Good explanation and good instruments.Thanks a lot.

[@jspencerg]

This is second try and second failure in accessing show notes. I'll try it on browser KZbin. Thanks for including the references.

[@w2aew]

Works with Chrome here. What platform were you using that failed?

[@jspencerg]

@w2aew Hello, Android KZbin app would not view your notes. Used android Chrome browser. Worked fine. Thanks again for excellent lessons.

[@w2aew]

@@jspencerg Not sure why, they're just PDF files. Maybe the Android app doesn't like the long URL.

[@yoramstein]

Hello Alan. Years ago I came across Unijunction transistor which had also a negative region in its characteristic like the tunnel diode. Can you explain what is the function of the third "foot" and what circuits was it used for?

[@manishsharma7]

That's really old looking retro pad!

[@w2aew]

Yep, that clipboard is probably more than 50 or 60 yrs old - it belonged to my late uncle.

[@IceArdor]

Any chance you could draw the IV curve either with a scope in XY mode (with a current probe or transimpedance amp) or with an SMU?

[@user-yo4fj5wo3v]

Nice driver for a laser diode.

[@jtb8631]

Fascinating

[@sayantanmaiti2513]

What is the part number of this tunnel diode you're using???

[@Max-eo6vx]

Unbelievable instructions

[@VoidHalo]

Great video. I'm fascinated by negative resistance devices. It'd be great if you could cover lambda diodes. I found out about them recently and ordered some P channel JFETs so I could play with them.

[@Kennynva]

Looks similar to a crystal, like the 455 khz one in my Hallicrafters...in the alignment you adjust the coil to the dip in the crystal...or the center of the crystal..

[@JustSomeGuy1967]

Your videos are fantastic ! thanks

[@Kamtar34]

Great, I think that with your talent some video for total begginers would be nice too. You know just some fast sum-up of A,V,R,L,C and diodes. I wanted some video which would give some basic idea and motivation to study it more for few friends which knows only ohm's law but i found nothing.

[@w2aew]

Tomáš Polišenský I'll certainly consider doing some very basic videos.

[@hongbinbin24]

Thanks a lot! It is helpful.

[@kd5ozy]

Very nice. Thank you

[@jimmyjewell2195]

Isn't the oscillation from.the power supply trying to maintain voltage regulation?

[@anandparalkar]

Thank you for this tutorial on the tunnel diode. I would like to understand the oscillations that you demonstrate on the oscilloscope at minute 8. While the scope is showing oscillations, the ammeter and voltmeter do not show any oscillations. I have some questions: 1. Can I presume that the oscillations are too fast for the meters to capture? 2. However, if there are oscillations and the meters are averaging, how do we get a "stable" value on the meter that confirms to the V-I characteristics of the diode? That is, the ammeter shows a drop with increasing voltage in the NDR? The ammeter is averaging, shouldn't we get some "in between" value? 3. What causes these oscillations? (After all, we have only applied an external voltage source which gets the diode to a certain bias point within the NDR.) Sorry, but then, I am just confused about the mechanism of the oscillations without any external components. (The oscillators shown later in the video have external components that help in causing the oscillation.)

[@w2aew]

Anand Paralkar Yes, the oscillations are too fast for the meter to respond to. The voltage/current is oscillating back and fourth between the peak and valley points on either side of the NDR region. The duty cycle depends on where I've got the DC bias. The meter is showing the average, thus follows the duty cycle change, which is why it does follow the basic shape of the IV curve. The oscillations are caused by the inductance and other parasitics of the test leads and test equipment, and even the resistance of the leads. Negative resistance devices can very easily cause these types of oscillations without help from additional reactive components.

[@anandparalkar]

***** Thank you for taking the time to reply! Much relieved to see that I was atleast thinking/suspecting in the right direction. :) Thanks once again for all your wonderful videos.

[@stevenbliss989]

Great lecture as always, THANK YOU! btw, CRAZY diode! :)

[@asunasposibol]

Could this be used for a time domain reflectometer?

[@royvanstraeten3215]

Again a great explination...thanks

[@yoramstein]

Hello Allen great video. I have seen in many Tektronix scopes that 2 tunnel diodes were used as Triger switch. Can you (will you) explain in a video who they did the work. (pre firing, firing, biasing as triggers are set to differend levels)?

[@kb7skb]

Thank you Alan! I always look forward to your videos. Very interesting and informative. I appreciate your time!

[@w2aew]

Thanks!

[@TheDoblink]

Very very good teacher!

[@Brian_Of_Melbourne]

Hi Alan, I just found out about something called a "Shockley Diode". It has a similar IV curve to the tunnel diode. Perhaps it would make a good subject for a future video?

[@michaelrockinger]

excellent video. now the hunt for tunnel diodes begins. nothing at the usual suspects: mouser, reichelt,...

[@yifeipei1862]

What is the model of tunnel diode used?

[@mohdnasir5140]

Page 76 AU (Astron) = Abbrev for astronomical unit. AU diode (Electronics) = See backward diode.

[@mohdnasir5140]

Page 330 diode (Electronics) = (1) Simplest electron tube, with a cathode and anode; used because of undirectional and hence rectification properties. (2) Semiconductor device with similar properties, evolved from primitive crystal rectifiers for radio reception.

[@dnshable]

wonderful video

[@miketoreno4969]

Can you do please sir a video about the lambda diode or about the impatt diode.

[@w2aew]

It's on my loooooong list of future topics...

[@rezokobaidze8501]

thanks a lot

[@mihajlopetkovic2003]

Why do we have two diodes in the second circuit which are connected across the 12 V and the base of the transistor?

[@w2aew]

It is just to setup a bias voltage on the base of the transistor that is a fixed ~1.4V below the 12V rail, which puts a fixed ~0.7V across the emitter resistor, which in turn makes the transistor source a constant current.

[@dalemyers9265]

2:31 into the vid. i'm thinking it might make a dc to dc power supply. like those in 12 to 14.2 volt mobile tube amp applications. where most run to-3 case transistors for the large load switching. the tunnel diode would be used for a reference signal generator. then a simple amplifier would boost the signal to the supplied 12-14.2 volts to function the high voltage step up transformer. just a thought.

[@w2aew]

dale myers Just remember that tunnel diodes are rare, low power, and fragile devices. Maybe not very well suited to a switching power supply.

[@dalemyers9265]

as i mentioned: i may not have been totally clear, the signals from the diode curcuit wouldn't be employed to power the transformer. it would be use as a signal generator, signaling an amplifier stage. to modify the supplied automotive power to a transformer, for the tubes bias, heater and plate voltages. and at a frequency of one meg. it wouldn't be as audible as the average mobile tube amp, referring to that all so pesky squeal.

[@w2aew]

dale myers Understood. I guess I was trying to say that there are less expensive, less exotic ways to create a 1MHz oscillator without using rare (expensive) tunnel diodes.

[@PerchEagle]

Really nice video .. I really enjoyed it.

[@mikeleo9463]

A question,are tunnel diodes sensitive to static electricity?It seems that their PN junctions are very delicate.

[@qwaqwa1960]

Might that be an HP-15c in the shot...? :-)

[@w2aew]

Yes, of coarse!

[@luisdalbianco3920]

What diode tunnel do you use? Tenkius. LU3UAE

[@AB-yu2tj]

Thank you. Is that metcall on your rework station are. I love to see a video on your soldering and rework tools.

[@w2aew]

Yes, that is a Metcal soldering station - I love that thing!

[@AB-yu2tj]

@@w2aew they are really good. I think I have the same tweezer, pencil and desoldering. But couldn't take a good look to see everything. I really like my metcal pencil, not crazy about their desoldering unit, It's good though. I finally got the pace prc 2000 90% complete I like the pace desoldering, Especially if it's connected to auxiliary vacuum pump. Metal soldering units matched with the correct tip is something else though specially for intricate stuff... It's been good thanks for replying. Looking forward to watch more videos from you

[@w2aew]

@@AB-yu2tj I only have the pencil and talon tweezers. I don't have any of the Metcal desoldering equipment. The only desoldering tools I have are a Haako 808 and assorted spring-loaded solder suckers.

[@dmitry926]

What is the cause of the oscillations when only the tunnel diode is connected to the circuit?

[@w2aew]

Many circuits become unstable with a negative resistance. Normally, when the the voltage across a decreases, the current drawn also decreases. This device has a negative resistance region - when the voltage decreases the current increases and vice versa. This leads to instability in many circuits.

[@divya7520]

Hi, thank you for very good video on tunnel diode working. I would like to know the reason behind negative resistance region in I V characteristics. The initial peak rise in current is due to tunnelling effect. But what actually happens in diode or what makes the diode to exhibit negative resistance?

[@w2aew]

There is a brief description on this wiki page: en.wikipedia.org/wiki/Tunnel_diode

[@davidharper1152]

Wow... an HP-15C sitting in the background... Nice

[@w2aew]

Still my daily go-to calculator.

[@olepetter7038]

Very informative, thank you. Have you touched on step recovery diodes yet?

[@w2aew]

***** Not yet, other than I reference I might have made to them when doing the video on the Comb Generator.

[@rohithkumar1688]

This is how we should be taught at colleges. Thanks for the video, well explained

[@BasilBadger]

My electronics teacher in 8th grade showed us a circuit made from a few transistors which behaved like a tunnel diode. Does anyone have such a diagram?

[@w2aew]

You're likely thinking of a lamda diode circuit - see here: en.wikipedia.org/wiki/Lambda_diode

[@xiaominglu9814]

Can you please explain how the current source circuit in your video actually works? I cannot understand why this is a so called current source? Thanks

[@w2aew]

The two diodes set up a fixed voltage on the base of the transistor, which puts a fixed voltage across the 100ohm emitter resistor. A fixed voltage across a resistor results in a fixed current. Since the emitter current and collector current are virtually the same, the collector becomes a source of a fixed current - thus a current source. Check out my video on current sources: kzbin.info/www/bejne/roOTg5mjorebetk

[@Kennynva]

Does the frequency change this dip, or just the amps...

[@TruthWillSF]

10:21 - 11:49 ❤️

[@copernicofelinis]

Well, that's totally unexpected! After only little more than five years, the links to the tekwiki documentation are all dead. Have they been transferred somewhere else or are they gone for good?

[@w2aew]

I fixed the tekwiki links.

[@copernicofelinis]

@@w2aew thanks! Firing up my downloader!!!

[@ajoytamhane6297]

Thanks a lot for the nice video. This is the first time I have seen a tunnel diode in action. What was the part nos of this diode?

[@w2aew]

I don't know the original manufacturers part number of this diode. All I have is the Tektronix stock number (Tek didn't manufacture it).

[@a1fliema1fie]

Do they have a use in modern circuit design or are they now a historical curiosity?

[@L2.Lagrange]

7:21 Do you happen to remember the frequency of that oscillation?

[@w2aew]

I don't recall, but will say that the oscillation frequency will be highly dependent upon the parasitic inductance and capacitance of the connected equipment.

[@push_pull_calisthenics]

great video, very informative :)

[@jlfqam]

Thanks again for another instructive video, Inside the Negative Differential Resistance Region, where the oscillations take place if I understood well, I guess the diode is in a state that is liable to be more easily affected by an external magnetic field and it may show up as changes in the oscillation frequency. Is it possible to test that in the circuit you used for the video?

[@w2aew]

jlfqam I'm not sure - it would be worth trying...

[@jlfqam]

***** Thanks, I found a couple of manufacturers of Tunnel diodes, made of Ge instead NJ Semiconductorsa and Advanced Semiconductor I did not ask for availability, just searched in their website database njsemi.com/parts/?search=1n2927 download.njsemi.com/1N2927,A%20-%201N2934,A.pdf www.advancedsemiconductor.com/pdf/1n2927.pdf www.advancedsemiconductor.com/cgi-bin/search?pattern=1n2927&submit.x=13&submit.y=15

[@w2aew]

jlfqam Good to know, thanks for posting those links!

[@geoden1645]

The I/V curve of a tunnel diode seems very close to that of a Gunn diode which is often used as an oscillator at microwave frequencies. Can the tunnel device reach similar high frequencies?

[@w2aew]

GeoDen Yes it can.

[@davidgrey943]

Hi very interesting discription on Tunnel diode operation,I have always wondered how they operate. Never ever been able to purchase or find Tunnel diodes here in New Zealand and under stood that they no longer were manufactured because there technology had been superceded by the technology we have today. Could you please let me know of a supplier of these because I am under the impression the are very costly. Regards David Grey

[@w2aew]

David Grey They are very costly because they are rarely used these days. I have been told that people have found some old Russian tunnel diodes on eBay for about 6 or 7 US dollars, but I haven't looked myself. I am not aware of any manufacturers that are making them anymore, but it is possible that there may be some small boutique fabs that can still make them.

[@Bdix1256]

Yes they are made in the us. We make them at m-pulse microwave.