tlfong014886Mon 15:46Now I have tidied up my hardware test setup. The foot print of the proto board is only of A2 size (15 x 22cm). So that in our maker’s club, each two participants can sit socially distant in front of a desk and do the experiment. They can also borrow the test kit and do their covid-lab-from-home experiment.

tlfong014886Mon 16:38Now about the I-V graph confusion. I very much agree with you that for two variables graph such as ours: (1) Current It is dependent variable, so should be represented as the Y-axis (ordinate), (2) Voltage Vt should be represented as the X-axis (abscissa). And as I pointed out earlier, the Vt range is too wide for Excel to draw a graph properly, So I tried to invert the X-Y graph to Y-X but the result is no good. Now I am thinking of drawing two graphs,(a) before the Vt for Ipeak, (b) after the negative region jump over. But I have little confidence that I am doing the correct thing. So I am uploading the Excel worksheet to my GibHub site，　．．．My GitHub site address is:github.com/tlfong01/…My GibHub’s licence is MIT. So you are free to download anything there to try things out. Later I will upload my python programs of ADC MCP3008/3201/3208 for the voltage conversions of the differential voltage across the Tunnel Diode (to get It vs Vt). Then I can ask Rpi4B Thonny python to plot the IV curve, without stupidly taking any manual readings using multi-meter, and use Excel later.  6 hours later… tlfong014886Mon 22:19Before trying the triangle wave sig gen, I am testing another tunnel diode part number 2SB4 sample #1. I happily got reasonable measurements, as shown below:

This time I did not waste my time trying to plot a complete curve using Excel, because I said earlier, the voltage range before jump over is 0~20mV, and after jump over is 486 mV ~ 500 mV, with stable increase of It around 1.88 mA. This time it is not a clear cut jump over, but can use adjust PSU to get unstable readings such as 194, 206, 221, 241, 250 mV. tlfong014886Mon 22:54Now I am randomly browsing EE SE’s old Q&A in the past 7 years or so, to get a rough idea of the EE SE guys here have been discussing. As I have expected, a Q&A forum are for short questions and short answers, so no deep level knowledge and skill can be covered. One useful thing is that I can find good reference pointer. An example if the 60 year old GE manual on tunnel diode.I skimmed the guide and I am glad to know how the engineers 60 years ago are doing R&D and enggr applications then. This is the guide and I skimming. I found the following topics useful: curve tracer, oscillation design, specification examples.Tunnel Diode Manual (including Curve Tracer, Oscillator Design, Load Line, Specification) – GE 1961
archive.org/details/…
ia902701.us.archive.org/3/…Corrected Links – Tunnel Diode Manual (including Curve Tracer, Oscillator Disgn, Load Line, Specifiction) – GE 1961
(1) archive.org/details/…
(2) ia902701.us.archive.org/3/…  8 hours later… Circuit fantasistTue 7:20Very interesting…  3 hours later… tlfong014886Tue 10:35I found my GitHub site on Tunnel Diode a bit too professional, and might scare the newbies away. So I decide to open a blog under my Google Account, dedicated to Tunnel Diode.My Tunnel Diode Blogger Blog’s address is:tlfong01’s Blog On Tunnel Diode
tunneldiode.blogspot.com  4 hours later… tlfong014886Tue 14:08Your suggestion of swapping X and Y axis is good. I also found I used the wrong Excel chart.

Also, because the X-axis values range is too wide, I need to split the X-axis into three, to make the values more readable. Many thanks again for pointing out my newbie charting mistakes.  3 hours later… tlfong014886Tue 17:21I have found the cause of the missing negative resistance portion in tracing the tunnel diode curve. I found that for the 2BS4 tunnel diode, there seems to be some oscillation in the 200mV to 270mV, 1.88mA range. Both causes are explained in the GE manual, as summarized below.

Ah supper time. See you later. Cheers.  10 hours later… Circuit fantasistWed 3:23Very interesting… Fig. 7.1 is exactly as the picture in my movie. Do you imagine where the load line is? Or you are waiting for Tony to explain to you what the load line is:)?  1 hour later… Circuit fantasistWed 4:43OK, I will say to you another wisdom as a reward for your curiosity. As you can see, there is no explanation about how the tunnel diode “jumps” over the negative resistance region in Fig. 7.1. (not only here but everywhere). They only say that it “jumps” but not explain how it “jumps”. Here is the geometric trick. Circuit fantasist5407Wed 4:59The intersection point between two curves (the IV curve of the tunnel diode and the load line) is what is called an “operating point”…If you look at my pictures, you will see that actually, it is an intersection point of two lines. Initially, the load line moves horizontally (translates) and the line representing the static diode resistance R stays immovable. When the intersection point reaches the peak, this line begins vigorously rotating while the load line stays immovable. So, the intersection point quickly moves (slides) along the load line… this is its trajectory..  6 hours later… tlfong014886Wed 11:14@Circuitfantasist Ah, (1) Tony’s Q&A site is down (today) for indefinite time. (2) The Q&A site is only for short Q (guide line: 70 word with a picture/datasheet) and short A (Tony’s A is only 50 words!). (3) I always prefer the Agile style, muddling through, chatting over, problem based learning/solving or case study approaches. I think a college level lecture and tutorial suits me better.Also I am a picture guy. So your explanation of negative resistance jump over and load line is too abstract for me. So I prefer the following picture rather than abstract description:

USC’s Prof Khan actually shows a series of slides/steps explaining the ideas of simple load line before finally arrive at the tunnel diode load line. His explanation of the TD I-V curve using a series of pictures (it would be nice to create an animated GIF, as I suggested) is also very good. I will show you the JPG/GIFs later  2 hours later… tlfong014886Wed 13:03Now the animated GIFs we can borrow.

  4 hours later… Circuit fantasist5407Wed 17:23@tlfong01 Hi! The picture representing the unstable point 2 is nice… There is only a “small” problem – there is no such point:) During the “jump”, the operating point does not pass through this place (point 2 does not belong the the trajectory). So, the picture is simply wrong. Please read carefully my expalnations about the bistable mode of the negative differential resistance – en.wikibooks.org/wiki/…. tlfong014886So I have set up PCF9851 ADC/DAC to do the tunnel diode I-V curve tracing. Earlier I wrongly though that I needed a high frequency sweep of 200kHz, 0~1V, to catch the fast jumping over the negative resistance region. Of course the electrons quantumly tunneling through the P-N barrier do it in no time, but we can plot the curve point by point as slowly as we like.In other words, I can use Rpi Thonny python to ask the PCF9851 analog output at a voltage level, and take our time to use two channels of the ADC to get the differential voltage across the tunnel diode. Circuit fantasist5407Regarding the blog… I think it is good to keep it in parallel with other forms of publishing (SE and Codidact) because there are a lot of visitors and there are discussions…I consider this phenomenon (and others circuit phenomena) at a “functional level” only… like in my WB story about NDR.Let’s return to the “magic” point 2 located at the negative resistance region… You can ask Tony to show this point in his simulation… if it exists… Try it, maybe this time it will answer you… tlfong01@Circuitfantasist Ha, thanks for pointing out my silly mistake of the non existent Point 2. Actually I am losing confidence of my thinking what is going on. Tell you one joke, I once mixed up the curve as a picture of the P-N junction, ie, left part of the graph is the real world P region, and right part is the real world N region. 🙂 Circuit fantasistI suggest to you to ask such a question in SE EE (and add it to your question in CoDidact) with this picture attached… I will answer with pleasure to you… and, in return I will probably get a lot of -1s … 🙂It will be a big “show”… tlfong01Are you talking about the USC Prof Khan’s beautiful picture about the Point 2? Perhaps I would spend more time studying his lecture, especially on the load line stuff, and ask newbie questions later. In the mean time I will start basic testing of the AD/DA module PCF9851. Circuit fantasistWed 17:36This is not your fault. I’ve seen this drawing since time immemorial, in the 80’s maybe. That’s how they explained it in the textbooks and that’s how my teachers taught it to me.Exactly, I am talking about this beatiful picture… tlfong01Ha, so the fake Point 2 is a third generation mistake! Circuit fantasist5407I remember, it was somewhere 20 years ago, I really wanted to know exactly this – where the operating point moves when it “jumps” … its trajectory …And I started asking my former teacher … it was even during a department council … And he answered me in this way and started looking at me badly because of my insights … tlfong014886My mind is still in a confusing state. I also forgot what you said about your Lancaster Elegant Simplicity transformer + 1k resistor + tunnel diode + Tektronic scope curve tracer. I have not kept a record of the deleted comments. It would be nice if you can give again the links of the your movies, Lancester stuff, I was sleeply when chatting those unthinkable stuff. Circuit fantasist5407en.wikibooks.org/wiki/… Read this explanation for the first “jump” and see how the point moves along the load line. But here it is horizontal, because I am examining the tunnel diode through a current source. In your case with a resistor, the load line will not be horizontal but inclined to the left as shown in the figure.🙂 tlfong014886By the way, do you also have any document on testing the ordinary diodes, like 1N4048, 1N4001 etc? I think I am over ambitious and running too fast. I am thinking of using my PCF9851 AD/DA to plot 1N4148, getting a smooth non broken curve, then go back to do tunnel diode.Ha, I need to first read carefully the load line stuff, understand it inside out, before reading you unreadable hard stuff, I mean your tunnel diode WikiBook. Circuit fantasistWed 17:49I have pictures and movies from the laboratory… Here are my students in the lab yesterday – photos.google.com/photo/…. But this was the last. From next week we only go online. tlfong014886There you are, the “No sweep, but point by point, python programmable, tunnel diode I-V curve tracing hardware setup, …

Circuit fantasistCompletely in the spirit of the new time …. Okay, I’m leaving you now and I’m going to do some tasks. It’s almost noon here now. Surely it’s evening there? tlfong014886Thanks for the movies, I will watch them later. It is almost supper time. I will jog a bit to settling down my overheated little brain, and eat, .. See you later.Ah I forgot one thing, that is about the remote online physics lab in an US college, where their students can remotely turn the “knob” of real instrument in the lab and get the results. I should search the link and put it in the tunnel blog. No my Secret Plan – The reason that I divert from the first version of using manual digital button to adust PSU for Vt, and also the triangular sig gen is that they cannot control remotely.Now my last version is Rpi python controllable, so I can set up a web server, with a web cam etc, and my bad lock down maker friends can use their smart phones, log to my “lab-from-home” show of electrons jail breaking through the tunnel of a diode, quantumly, in no time, ｓｏ　ｍｙ　ｂａｄ　ｆｒｉｅｎｄｓ　ｗｏｕｌｄ　ｎｏｗ　ｒｅｓｐｅｃｔ　ｍｅ　ｍｏｒｅ　ｔｈａｎ　Ｉ　ｄｅｓｅｒｖｅ，　．ｓｏｒｒｙ　ｆｕｎｎyｙ　ｃｈａｒ　ａｇａｉｎ，　ｂｙｅ．  3 hours later… tlfong01Wed 21:14@Circuitfantasist Your photo library link seems broken. Please send another one. Circuit fantasistphotos.app.goo.gl/…Can someone look at our chat? Or, he has to join it first? tlfong014886Wed 22:13Now I have drawn the schematic, before doing python programming. tunneldiode.blogspot.com/2020/…@Circuitfantasist Ah, I think this chat room is open to all users．Ｈｏｗ　ｃｏｍｅ　ｊｕｓｔ　ｏｎｅ　ｐｈｏｔｏ？Ａｈ，　Ｉ 　ｔｈｉｎｋ　ｎｅｅｄ　ｔｏ　ｒｅｇｉｓｔｅｒ　ｔｏ　ＥＥ　ＳＥ　ｆｉｒｓｔ．Ｓｔｉｌｌ　ｆｕｎｎｙ　ｃｈａｒａｃｔｅｒｓ．　Ｉ　ｈａｖｅ　ｎｏｔ　ｆｏｕｎｄ　ｏｕｔ　ｈｏｗ　ｔｏ　ｇｅｔ　ｒｉｄ　ｏｆ　ｔｈｅ　ｆｕｎｎｙ　ｃｈａｒａｃｔｅｒｓ．　Ｐｅｏｂａｂｌｙ　ａ　Ｃｈｉｎｅｓｅ　Ｗｉｎｄｏｗｓ　Ｌａｎｇｕａｇｅ　ｂｕｇ． tlfong014886Wed 22:39Now I am using FireFox and so far so good. I found my Chrome write funny characters in EＥ．．．　Ａｈ　ｂａｄ　ａｇａｉｎ，　ｅｖｅｎ　ＦｉｒｅＦｏｘ　ｈａｓ　ｐｒｏｂｌｅｍｓ，　ｂｙｅ．Ｙｏｕ　ｍｉｇｈｔ　ｌｉｋｅ　ｔｏ　ｉｎｖｉｔｅ　ｙｏｕｒ　ＥＥ　ｓｔｕｄｅｎｔｓ　ｔｏ　ｊｏｉｎ　ＥＥSE and, OMG, normal char again.You might also like to invite your students to visit my newly opened tunnel diode blog. They are most welcome to browse and leave messages and ask questions. The funny chars seems gone. I will go back to Chrome and try my luck again.Ｓｔｉｌｌ　ｃａｎｎｏｔ　ｇｅｔ　ｒｉｄ　ｏｆ　ｆｕｎｎｙ　ｃｈａｒ　ｉｎ　ＥＥ　ＳＥ．　Ｐｅｒｈａｐｓ　Ｉ　ｓｈｏｕｌｄ　ｔｅｌｌ　ｅｖｅｒｙｂｏｄｙ　ｍｙ　ｔｕｎｎｅｌ　ｄｉｏｄｅ　ｔｅｓｔｉｎｇ　ｐｌａｎ　ｉｎ　ｔｕｎｎｅｌ　ｄｉｏｄｅ　ｂｌｏｇ．  10 hours later… tlfong01yst 8:40Just checking Chinese Win 10 Funny Character Problem. Last evening I found both Chrome and Firebox have intermittent problem. I thought this morning I might need to switch to Rpi4B Chrome. But now I don’t find this problem. I will come back and check later. No need to reply. Cheers.  2 hours later… tlfong014886yst 10:43When polishing my long tunnel diode question in CD, @circuit brought out a couple of inspiring ideas, one of which is “Lancaster Elegant Simplicity”. This part was deleted, so I need to google to recover: tinaja.com/glib/elesimp.pdf. I remember I skimmed the idea was impressed by the samples, including the “Schmitt Trigger (HC14)” oscillator.I did agree the simplicity was elegant, so I said I always recommend system integration newbies to use the Occam Razor principle, and mentioned that I would use it in my proposed tunnel diode plot the I-V curve experiment.Lancaster gave an example which I think using the hystersis feature, which I think might be useful when exploring the tunnel diode oscillator, because I found that tunnel diode curve, after jumping over the negative resistance, can go back to part of the neg res region which we cannot walk by before jumping over. But I am not sure if it is useful. Anyway, the Schmidtt Oscillator:

Actually I was thinking of using the Schmidt oscillator’s cap’s output as the Vt voltage source to power the tunnel diode, to replace the triangular wave sig gen when poltting the I-V curve.Lancaster also points out that his elegant simplicity is also related to ideas such as Occam’s Razor, Schumacher’s “do more with less” and Buckminster Fuller’s “Appropriate technology“. I also pointed out the KISS principle which I learned when doing computer programming.Then I pointed out it is not necessary (or overkill) to use an instrumentation grade op amp, because when exploring the tunnel diode missing neg reg region, we only need to find out the cause and answer my long question, not to do any precise experiment. Perhaps my question title is leading, but I do point out that my crux of the mater question is the root cause of the jumping over and no measurement.As I said earlier in this chat, I already found the cause in GE’s 1962 tunnel diode manual. So the next step of the answer is verify that my guess is correct. tlfong01yst 11:44Ockham’s Razor principle of the most fundamentally direct explanation often ending up the most correct. Or Einstein’s “Always seek out the simplest possible solution – but none simpler“. tlfong01yst 12:08So I think PCF8591 for tunnel diode I-V curve plotting is “As simple as possible“, “As cheap as possible“, “As small a possible“, and “As newbie frienly as possible”  5 hours later… tlfong014886yst 17:34Now I have started developing the python program to generate the Vt for plotting the Tunnel Diode TD. So it is a long project, perhaps over 3 months, with a 2,000_ line program, perhaps also a web site for remote lock down lab from home experiment.So the plotting the TD curve is just a very first step to test the water. If TD is OK, I might try other diodes. It is basically a non profit making, open source (hardware and software) CoLearn educational at community college, technician, hobbyist, maker, Raspberry Pi / STM32/ESP32 based level project.So the project is too big to fit a Q&A site. But our strategy is breaking the project into smaller, correlated pieces. I know the ideal Q&A for EE　might be very short. For example, like a short answer, “Which document should a hobbyist read to research into Tunnel Diode?“, Then an appropriately short answer is “Check out Generic Electric’s TD User Guide 1962, with a link to their archived documents.Ａｈ　ｓｕｐｐｅｒ　ｔｉｍｅ，　ｓｅｅ　ｙｏｕ　ｌａｔｅｒ．　Ｊｕｓｔ　ｎｏｗ　Ｉ　ｓｕｒｐｒｉｓｉｎｉｎｇｌｙ　ｆｏｕｎｄ　ｔｈａｔ　Ｉｆ　Ｉ　ｔｒｙ　ｔｏ　ｔｒｙ　Ｃａｐｉｔａｌ　Ｅ　ｂｙ　ｐｒｅｓｓｉｎｇ　ｔｈｅ　Ｓｈｉｆｔ　ｋｅｙ　ａｎｄ　Ｅ，　ｔｈｅｎ　ｔｈｅ　ｆｕｎｎｙ　ｃｈａｒａｃｔｅｒｓ　ｊｕｍｐ　ｏｕｔ．　Ｎｅｅｄ　ｔｏ　ｅｘｐｌｏｒｅｓ　ｌａｔｅｒ．　Ｉｎｄｅｅｄ　ａｎｎｏｙｉｎｇ，　Ｃｈｅｅｒｓ．  4 hours later… Circuit fantasist5407yst 22:10I begin answering… Regarding the Schmitt oscillator, look at my explanation here where I have shown that there is no negative feedback in this op-amp circuit (although there is a physical connection between the op-amp output and inverting input)…For your purposes, the version with 2 op-amps is more suitable. tlfong014886yst 23:00Ha, I am too weak in op amp to understand both the Schmitt and the uA741 x 2 function generator. As usual, I will try to cheat and find an function gen IC to do the job. But I am not too sure to find, or actually the same ICL8xxx module.Anyway, I have already started programming the PCF8591’s DAC part, which is more flexible because I can generate any analog voltage level at any point in time. But only 50% make I can make it.As a contingency plan, and also make thing scalable and concurrent, I am also considering the digital potentiometer (I guess it is more precise and looks like a pro, while PCF8591 looks like a toy. Again, it might take a long while to read the datasheet.Anyway, my ambitious plan is to write a python program to control two ADC’s and plot two tunnel diode I-V curves at the same time, and also display two curves in the scope at the same. Perhaps I am dreaming too early. Anyway, bed time, see you tomorrow.And I did consider using NE555 timer module to generate the triangular wave. I remember NE555 has one ore two op amp comparators inside the chip, so lazy me will not consider the op amp way. I think I am some how op amp allergic. 🙂  4 hours later… Circuit fantasist54072:46TL Fong, I hope you already have realized that the IV curve does not depend on time. So, you can measure it by any kind of input signal (triangle, ramp, sine, etc.) Also the frequency of the signal does not matter … and as I already wrote, you can even use a DS signal (for example, produced by a potentiometer) if the scope is digital with memory. Since scopes in my laboratory are analog type, I use the simplest AC signal generator – the mains voltage reduced by a step down transformer.Of course, the most professional solution is to generate the signal through a microcontroller and DAC as you have decided to do. I realized this idea in 1986 through a personal computer (MICROLAB system). Circuit fantasist54073:03This was an AD interface implemented by 4 12-bit DAC 1200 (National semiconductor) and an ADC with 4-input analog multiplexer – see the block diagram and the construction of the laboratory setup.Here is an example of measuring an IV curve of a Zener diode. I had put a lot of such links under your question but Olin deleted them. Circuit fantasist54073:36Regarding the forum… The problem is not short questions… neither short answers… neither long discussions… These are just forms of knowledge transfer. It is not the form that matters, but the content. The main problem is the envy that arises in those who know but do not understand circuits. It makes them interrupt such valuable discussions under questions and answers with meaningless remarks such as, “This is a site for questions and answers, not for discussions,” and more…  The last message was posted 5 hours ago.