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.

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!

That was the best instruction I have witnessed to date.

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.

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

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

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.

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. ;>)

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

Excellent and informative as usual. Keep them coming.

Have not thought about those in a while. Refreshing!

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.

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

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

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

Clear and simple as always, thanks

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!

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

thanks for the tutorial !! enjoy all your videos

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

Nice job Alan. Thanks.

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

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. :)

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.

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.

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

Great video, great explanation. Thanks for making it.

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

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.

Good explanation and good instruments.Thanks a lot.

Your videos are fantastic ! thanks

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.

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 ;-)

THAT thing should be called a goofy junction.

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

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

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

Very very good teacher!

Again a great explination...thanks

Really nice video .. I really enjoyed it.

great video, very informative :)

Very nice. Thank you

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!

wonderful video

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

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.

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,...)

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

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?

Thanks a lot! It is helpful.

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?

Fascinating

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.

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

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)?

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.

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

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

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

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

Unbelievable instructions

Awesome!

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

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?

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

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

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

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?

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

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?

Hey, fantastic video and explanation, thank you! A question - is it possible to use these tunnel diodes to still convert AC to DC (up to 12V) or is there any other effect above a certain voltage? also would it work with any frequency of AC? (talking up to 13,56 MHz)

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.

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..

I really enjoy your video's, they are very informative. But what hardware (sockets) do you use to plug components into? I would like to get some for when I am experimenting. Thanks again and keep up the wonderful video's. 73's WK4DX

thanks a lot

yes, Sir!

Could this be used for a time domain reflectometer?

Nice driver for a laser diode.

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

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

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?

Where do you buy tunnel diodes from? I searched Digikey for Esaki and Tunnel diodes, and came up blank?

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

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?

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

What is the model of tunnel diode used?

What specific diode were you using for your testing?

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

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

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?

Amazing ... you should go on tv

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

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

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

That's really old looking retro pad!

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?

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

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

Thanks again ditto the pin diode.

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.)