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62%+3−1Q&A How to plot the I-V curve of a tunnel diode?

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62%+3−1Q&A How to plot the I-V curve of a tunnel diode?

5 answers  ·  Question diodetunnelPost edited by user avatarOlin Lathrop‭ · 2020-11-21T21:11:48Z (21 days ago)

  • [](https://en.wikibooks.org/wiki/Circuit_Idea/Revealing_the_Mystery_of_Negative_Impedance)**_Question_**
  • _Brief description of the problem_
  • How to plot the I-V curve of a tunnel diode?
  • _Background_
  • I am curious to know how the tunnel diode works. So I googled and wikied and after a couple of hours reading, I found some related ideas:
  • (1) A tunnel diode shows the _negative resistance_ characteristics.
  • (2) A tunnel diode can be used to build a very high frequency oscillator.
  • _Problems encountered_
  • I have a very rusty EE diploma from Hong Kong Technical College, where I learned basic electronics circuit theory and practice. I once earned my living as a electronics technician. The electronics industry in my place sadly collapsed long long time ago. So electronics to me now is just a hobby, but I am still curious and interested to know more about electronics, and my recent interests are _negative resistance_ and _tunnel diode_.
  • I must confess that I do not have the prerequisite knowledge to understand the negative resistance theory, because I don’t have adequate solid background in ideas such as differential voltage, dynamic resistance etc, which I think are essential to fully understand the concept of negative resistance.
  • _Learning by doing_
  • A couple of years ago I was happy to learn the MIT offered free online courses including EE. So I took a foundation course, but I dropped out very soon, because could not keep up with the very fast pace of lectures and tutorials, and most important of all, I could not attend the hardware and software labs and experiments.
  • But one of the few things I learned from MIT is the motto: “Learning by doing”. My experience as an electronics troubleshooting is that there are theoretically abstract things which you might not fully understand if you only study the equations and graphs, but if you use a multimeter and to measure and display current and voltage values, and use a scope to watch the variables’ time dependence, then you learn faster, deeper, and remember theory longer. Another thing is that if you, say, design a circuit, try it, and if it does not work, but you learn from your failures, and as Thomas Edison says, “I have not failed. I’ve just found 10,000 ways that won’t work.”
  • _Research so far_
  • Now let me explain and summarize what I have been doing so far:
  • (1) Objective – Plot the I-V characteristic graph of a tunnel diode.
  • (2) I have already bought a couple of cheapy tunnel diodes (part number 2SB3, US$3 each)
  • (3) I have also got a couple of ordinary diodes 1N4148 to compare and contrast, sort of paring/swapping testing/caribration/troubleshooting.
  • (4) I have the following equipment to do the measurements:
  • a. A couple of chaapy US$4 or so, multimeters that can measure down to 200mV and 200 uA.
  • b. A digitally button adjustable 0V ~ 10V, 3A regulated switching power supply, in increments/decrements of around 0.01V (10mV).
  • (5) The setup and testing procedure are simple:
  • a. Connect PSU in series with a protective, current limiting resistor, and the tunnel diode.
  • b. Increase/decrease voltage level, in steps as fine as mV, and measure corresponding current values, as fine as 0.1mA
  • c. Plot the I-V graph, and day is done.
  • _Failure analysis_
  • Well, my experiment of course failed flatly, and that is why I am asking here for help. Originally I expected to get a I-V characteristic graph, as we see in all datasheet of rectifying or flyback diode, an exponential curve starting from origin, starting shallow, then goes steeper and steep as voltage increases.
  • I did expect that for the tunnel diode, there should be something weird in the middle of the curve, so called negative slope which denotes the negative resistance, …
  • Let me summarize the characteristic of the tunnel diode, before I describein detail why I failed:
  • _Tunnel diode 2SB3 datasheet summary:_
  • a. Ipeak voltage ~= a few mV.
  • b. Ivalley voltage ~= a ew hndred mV
  • c. Ipeak ~= tens of mA
  • d. I valley ~= don’t know cannot measure!
  • _Now the failure details is the following:_
  • a. As I increase voltage from 0 to IpeakV, the current increases as expected,
  • b. But once approaching the IpeakV, the current suddenly jumped from tens of uA to some 400/500mA. In other words, I just missed the most important measurements, those of the negative resistance region.
  • **_Now my questions:_**
  • Why I cannot measure the current I as soon as the gradually increasing voltage V enters the negative region? How can I tell the tunnel diode not to “skip” the tunnel?
  • **_Discussion_**
  • This is the very first question I submitted in CoDidact. Please feel free to comment or suggest to improve my question.
  • **_References_**
  • (1) [Negative Differential Resistance – @Circuit fanatsist, WikiBooks 2020sep05](https://en.wikibooks.org/wiki/Circuit_Idea/Negative_Differential_Resistance)
  • (2) [Circuit Idea Revealing the Mystery of Negative Impedance – @circuit fantasist, WikiBooks, 2020sep05](https://en.wikibooks.org/wiki/Circuit_Idea/Revealing_the_Mystery_of_Negative_Impedance)
  • (3) [Waveform Generator for Rpi3B+](https://raspberrypi.stackexchange.com/questions/96423/pi-hat-waveform-generator-for-raspberry-pi-3b)
  • (4) [ICL8038 Sig Gen 10Hz-450KHz sine-rectangle-triangle 12V ~ 15V](https://fr.aliexpress.com/item/32884149123.html?spm=a2g0w.search0302.3.33.9eed274eVDOtIR&ws_ab_test=searchweb0_0%2Csearchweb201602_0_10084_10083_10887_10307_321_453_322_454_10618_536_10065_317_537_10068_319_10059_10103_10884_10696%2Csearchweb201603_0%2CppcSwitch_0&algo_pvid=4ca8efc3-5304-4dfb-87d9-24f7b2e71173&algo_expid=4ca8efc3-5304-4dfb-87d9-24f7b2e71173-4)
  • (5) [DDS Signal Generator – Geoff‘s Projects](https://geoffg.net/SignalGenerator.html)
  • **_Appendices_**
  • _Appendix A – Negative Resistance Graph_
  • ![Negative resistance](https://electrical.codidact.com/uploads/LHi52PEN9QJidiCduW1jHp3u)
  • _Appendix B – The Test Circuit Design_
  • Actually the first problem that came up to my mind is how to get a stable voltage source to power the tunnel diode. I vaguely know that the test range should be between 0V and perhaps at most 1V, and the negative resistance region should be somewhere between 0.2V to 0.8V. This is just a wild guess, because I don’t have a datasheet.
  • I don’t have any low voltage PSU in hand, and using a simple voltage divider consisting of one resistor and one stupid analog pot should be face losingly damage my reputation, and all my bad maker friends would LOL.
  • So the first thing I considered is to use an op amp to step down from say, 0V to 10V to 0V to 10mV.
  • Ah, bed time, so I just upload my final design picture here (schematic later), and explain how I came to this quick and dirty, sloppy design tomorrow. 🙂
  • ![Test setup](https://electrical.codidact.com/uploads/yBTaLeqSQb4qQTKcn8Hqmc9f)
  • _Appendix C – Tunnel Diode 2BS3 Sample 2 Measurements and Curve_
  • _Notes_
  • a. Manual measurements not that accurate.
  • b. **_The negative resistance region is somewhere between 25 mV ~ 450 mV_**
  • ![plot curve](https://electrical.codidact.com/uploads/QvsSNkiCZ3cNj9ZZjKinse4V)
  • _Appendix D – @circuit fantasist’s Tunnel Diode Curve Plot_
  • @circuit fantasist’s experiment, explaining the tunnel diode is in bistable state, so the negative resistance region is not stable, resulting the tunnel diode flip from one stable state to another. In other words, the tunnel does following the I-V curve all the time, it is moving too fast, so not observable by my stupid human eyes, and not even by the fast 50MHz Tektronix scope, … 🙂
  • ![bistable state](https://electrical.codidact.com/uploads/wQTNomkPSBFrNBMbkf1WiE5h)
  • Appendix E – @tlfong01‘s Tunnel Diode Curve Tracer Circuit Design v0.1
  • I am thinking of using ICL8038 sig gen for the following reasons:
  • a. I now know that the tunnel diode 2SB3’s current is of order of a couple of mA, and the total sweep is only 0V to 0.5V (as I said earlier, I guess the negative resistance region is between 24mV and way below 450mV)
  • b. ICL8038 sig gen can sink 25 mA max, so there is no worry that the signal source would be overloaded and it signal distorted.
  • ![ICL8038 sig gen](https://electrical.codidact.com/uploads/D5zvTXgF3B2TdErFjbNRjuDn)
  • _/ to continue, …_
  • I am trying to understand tunnel diodes by experimenting with them. Research tells me they can have negative resistance, and can be used to build a high frequency oscillator. Tunnel diodes are supposed to have this I/V characteristic:
  • ![Image](https://electrical.codidact.com/uploads/RdYW4sCesiMuft6R45GaZhwe)
  • I don’t really understand negative resistance, so I thought plotting the I-V characteristics myself would help me understand. Unfortunately, that didn’t work.
  • What I did:<ul>
  • <li>Connect PSU in series with a protective, current limiting resistor, and the tunnel diode.
  • <li>Increase/decrease voltage level, in steps as fine as mV, and measure corresponding current values, as fine as 100 &micro;A.
  • <li>Record each point on a graph of current as a function of voltage.
  • </ul>
  • Here is my test setup:
  • ![Test setup](https://electrical.codidact.com/uploads/yBTaLeqSQb4qQTKcn8Hqmc9f)
  • As I increase voltage from 0 to IpeakV, the current increases as expected. Once approaching the IpeakV, the current suddenly jumped from tens of &micro;A to some 400/500 mA. In other words, I just missed the most important measurements, those of the negative resistance region.
  • Why can I not measure the current as soon as the gradually increasing voltage V enters the negative region? How can I tell the tunnel diode not to “skip” the tunnel?

diodetunneldiodetunnelPost edited by user avatartlfong01‭ · 2020-11-21T14:13:24Z (21 days ago)Post edited by user avatartlfong01‭ · 2020-11-21T14:03:41Z (21 days ago)
start a new Appendix on tunnel diode curve tracer design using ICL8038 v0.1Post edited by user avatartlfong01‭ · 2020-11-21T08:51:08Z (22 days ago)Post edited by user avatartlfong01‭ · 2020-11-21T08:42:30Z (22 days ago)Post edited by user avatartlfong01‭ · 2020-11-21T08:40:00Z (22 days ago)
added sig gen referencesPost edited by user avatartlfong01‭ · 2020-11-21T08:36:22Z (22 days ago)Post edited by user avatartlfong01‭ · 2020-11-21T07:51:08Z (22 days ago)Post edited by user avatartlfong01‭ · 2020-11-21T05:38:00Z (22 days ago)
Edited the titlePost edited by user avatartlfong01‭ · 2020-11-21T05:36:45Z (22 days ago)Post edited by user avatartlfong01‭ · 2020-11-21T05:33:21Z (22 days ago)
Added I-V measurements and a plotPost edited by user avatartlfong01‭ · 2020-11-20T15:25:54Z (22 days ago)Post edited by user avatartlfong01‭ · 2020-11-20T09:22:15Z (23 days ago)Post edited by user avatartlfong01‭ · 2020-11-20T09:08:29Z (23 days ago)Post edited by user avatartlfong01‭ · 2020-11-20T09:06:35Z (23 days ago)Post edited by user avatartlfong01‭ · 2020-11-20T09:03:29Z (23 days ago)Initial revision by user avatartlfong01‭ · 2020-11-20T08:41:09Z (23 days ago)

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