tlfong014930Dec 6, 9:52Often my answers are on new things which needs constant updating/editing. So I am editing my answer often, but then it is not welcome by newbies, because often then follow my suggestion and DIY a working project, but later they find I introduce any new, better, and cheaper device, … So I usually try ti make less edits, by reminding myself John Maynard Keynes saying “In the long run we are all dead”, cheers.@Circuitfantasist Yes, my Blogger posts are very organized. I tried to label them to make them easier to search and group. Another way is to set up a new blogger account, eg, AD5933 blog only for this device. This is why I originally in CD, asked the question, “How to plot the I-V curve?”, and even give all the details I have researched, the hardware setup, why I failed etc, so a the SO say, laser sharp focus on the problem, …Ah, morning tea time. See you later. Cheers.Ah, before I go, I forgot to suggest Quora: “What Is Quora & Why Should You Care?”
searchenginejournal.com/…. I often found easily high quality answers there, because they would briefly mentioned their academic qualifications and experience at the end of their answer, also in their profile.Ah I gorgot to give an example, a short answer in python: quora.com/….  3 hours later… tlfong014930Dec 6, 13:04This is an example of the Q&A about Tunnel Diode in Quora. The author gives a short answer in Quora and links a long article in his Blog. This is what I am considering doing:Short answer in EE SE Q&A, with a link to my blog’s long answer, which I am update/edit as often as I wish.Draw the i-v characteristics of tunnel diode and explain with proper energy diagram? – Himanshi Gupta, 2016dec12
quora.com/unanswered/…

About Himanshi Gupta
Studied at Kurukshetra University, Lives in New Delhi, 784.1K content views235 this month

Tunnel Diode And Tunnelling Effect – Ajay Kumar, Analyse A Meter 2016mar14
analyseameter.com/2016/03/…  2 hours later… tlfong01Dec 6, 15:03An article on how to finish your blogger project: tunneldiode.blogspot.com/2020/…tlfong014930Dec 6, 15:15I am still read references on tunnel diode, and still not finalizing my question. I always remember SO/SE’s guideline on up/donm vot a question: ***This question shows research effort. It is useful and clear***” – SO/SE Upvote/Downnovt tip. So I am reading yet one more reference on tunnel, and I found this one very good:
tunneldiode.blogspot.com/2020/…tlfong01Dec 6, 15:56Now I have found the two articles by Hackaday’s Yapo best answer my question: “How to plot a tunnel diode’s I-V curve, especially in the NDR region?“. I would give 10/10 marks for Yapo, and -10 marks for ALL the fake, rubbish non answers in CD.  1 hour later… Circuit fantasist5702Dec 6, 17:05TL Fong, thanks for the valuable thoughts! I completely share them; I have been using some of them for a long time. But in SE EE I had problems quoting my materials because they qualified it as “self-promotion”…Last night I wrote a short answer to your question where I explained the behavior of the tunnel diode in a fun way. I hope you like it. I will make a copy in my blog too. Cheers!  3 hours later… Circuit fantasistDec 6, 20:03Here is the copy – circuitstories.blogspot.com/…tlfong014930Dec 6, 20:33@Circuitfantasist Ah, about self promotion, you remind me one thing related to Olimex: (1) fongheart.blogspot.com/2013/…, (2) tunneldiode.blogspot.com/2020/…. Question: I remember Olimex was established by some university academics in Bulgaria, but I forgot which University. Do you know which one? Circuit fantasistDec 6, 20:56Interesting… I have never heard about it… How could I have heard like me dealing with basic ideas from the 19th century and they with miracles from the 22nd:)?  15 hours later… tlfong014930Dec 7, 12:13@Circuitfantasist Well, when I was 10, I heard about scientists in 1600’s doing experiments with frogs, using electricity as a signal to move the frog’s legs. Fast forward to 2010’s I was curious to know what is ECG. So I went to a hospital to do ECG, and later I had the opportunity to play with handheld and desktop ECG machines, so I spent some two hobbyist weeks learning how to do ECG.At that time, I google for ECG toys, and found a startup project called Bulgaria Olimex was selling cheapy EKG board, which I think it the first of its kind. I bought two Olimex ECG board and learned about how they design circuits using virtual ground using human right leg, and how to use low pass filters to eliminate high frequency noises, … , tunneldiode.blogspot.com/2020/…***  10 hours later… Circuit fantasist5702Dec 7, 22:19TL Fong, I have no experience in ECG circuits but I know they are very sophisticated. But I would be happy to figure out the tricks used in them. Here is how I have explained, with a lot of imagination and intuition, the so-called right leg driven circuit…As you can see, the idea was rated with 0 reputations while the elite received a dozen of them for a dry and formal explanation… This is a good illustration of Einstein’s thought that I used as a motto at the top of my Wikipedia user page.  14 hours later… tlfong014930Dec 8, 12:42Ｙｏｕｒ　ｒｉｇｈｔ　ｌｅｇ　ｄｉｓｃｕｓｓｉｏｎ　ｉｓ　ｇｏｏｄ．　Ｉ　ｆｏｕｎｄ　Ｓｃｏｔｔ　Ｓｅｉｄｍａｎ＇ｐｒｏｆｉｌｅ　ｉｎｔｅｒｅｓｔｉｎｇ：electronics.stackexchange.com/…　Scott Seidman
top 0.80% overall
＊＊＊Engineering Educator＊＊＊, Biomedical Engineering, Bioinstrumentation, Embedded Systems, Medical Devices, Design tlfong014930Dec 8, 13:07I noticed one difference between the EE SE answers and mine is that I focus on module level, or system integration problems, almost always never at lower op amp level. Take the ECG Q&A as an example, you see that I give a lot of references, and debugged demo programs, and real life example python programs.(1) Raspberry Pi 3B+ interface with Heart Monitor AD8232 using MCP3008 and SPI pins – Asked 1 year, 7 months ago, Viewed 4k times
raspberrypi.stackexchange.com/…

(2) How can Rpi read the MAX30100 / MAX30102 Oximeter? Asked 7 months ago Active 1 month ago, Viewed 2k times
raspberrypi.stackexchange.com/…  9 hours later… tlfong014930Dec 8, 22:14Now I have set up the I2C AD5933 module and found Rpi4B can detect it without any problem. Next step is to write a little python to measure the impedance.

tlfong014930Dec 8, 22:42About the right leg circuit, I remember the first article I read about the 10 lead ECG is based on the Einthoven Triangle – Wikipedia
en.wikipedia.org/wiki/…. The very clever guy invented this triangle the late 1800’s, and got a Nobel prize in medicine. I remember I spent a couple of hours clarifying the basic things, and explain to a medi guy how the triangle works, and how to memorize the meaning of the names of the 10 leads. One thing I was very impressed is the following: The 12 leads are placed on the serface of the body, but what is interpreted is the h…(see full text)Ah bed time, call it a day, see you tomorrow.  18 hours later… Circuit fantasist5702Dec 9, 17:00OK, you made me think again about the exotic right leg circuit… I needed time to remember the idea behind this odd arrangement. I will reorganize my answer there and will create a post here about it. Now I’m moving to the blog to reply to your interesting comments there. Maybe I will redraw the conceptual circuit diagram…  1 hour later… tlfong014930Dec 9, 18:00Yes, I think both of us need to take a break and look back what we have been chatting so far. I agree that you might need to redraw you conceptual diagrams, with more descriptions on the test setup etc (Step 2 of my selfie walkthrough below). The Right Leg cct might take you a long time, because it was designed more than one hundred years ago, and some terms are inconsistent with today’s usage.I agree with you saying that my blog is getting very messy, and it is difficult to search things. So I have decided to make a summary in the new post:tunneldiode.blogspot.com/2020/….I have been randomly hopping here and there, diverting aimlessly. Now I think your “Transformer + hand knob pot + scope” is in Lancaster’s Elegantly Simple style and indeed elegant, but it is difficult to understand. So if you can explain it with your new enhanced conceptual diagram should help tunnel diodes newbies a lot. In the mean time I hope my use of the triangular wave would hopefully get the picture as by Tektronix (Step 7).(removed)Ha, supper time. See you later.  2 hours later… Circuit fantasist5702Dec 9, 19:57TL Fong, It is a pleasure for me to read what you have written. I agree with it. You come out right – the right leg circuit takes time. I played with it because I lost something in my understanding. Here’s how I try to imagine it geometrically – photos.app.goo.gl/…, photos.app.goo.gl/….  9 hours later… Circuit fantasistDec 10, 5:06TL Fong, I edited my answer to the question about the right leg driven circuit. It would be interesting to make some “discussion” there. Also, I will copy it in my blog…  4 hours later… tlfong01Dec 10, 9:03Just a quick reply. Ah it would nice if you can copy it to your blog and I make comments there.  3 hours later… tlfong014930Dec 10, 11:50As I said earlier, I am more interested in hobbyist style system integration, eg buying cheapy ECG modulde from Bulgaria Olimax, open source bio sensor board designed Analog Devices and other well known brands. Then I make workable devices for fun, or let the newbies know how me, the hobbyist developer follow the CMU research paper, use their recommended AD5399, make a real device helping disabled persons with bio sensors, and AI software, …I am not interested at all in low level at op amp ccts, otherwise I would invest tons of hours reading research papers like to following:

  3 hours later… tlfong014930Dec 10, 15:06I ma reading you following answer on Schmitt ｔｒｉｇｇｅｒ　oscillator, because I am thinking of using the oscillator’s trnanglur ouput to power the tunnel diode when drawing the I-V curve.
electronics.stackexchange.com/…

I found you description of the amplifier too difficult for me. So I went to AAC (All About Circuits) for help. I found AAC good for low IQ guys like me　：）: tunneldiode.blogspot.com/2020/…(see full text)Circuit fantasistDec 10, 15:28OK, I ам startинг now my online lection… I will write to you later…  2 hours later… Circuit fantasistDec 10, 17:30“am starting”:)TL Fong, I have a feeling that you have some fear of the elite:)? tlfong01Dec 10, 17:47Ha, yes, the real elites in Physics.StackExchange trigger my inferiority complex. 😦  1 hour later… Circuit fantasistDec 10, 18:52circuitstories.blogspot.com/…  4 hours later… tlfong01Dec 10, 22:54Then I will listen to some inferiority complex healing music, or find some ***fake elites*** to beat them up. 🙂
youtube.com/…  4 hours later… Circuit fantasistDec 11, 3:19nice material about ECG  8 hours later… tlfong014930Dec 11, 11:30@Circuitfantasist Just now I skimmed my ECG project log and found the whole documentation file is about 350MB large. I am thinking of using AD5933 impedance tester to confirm some of my old experiment results. I quickly skimmed the basic stuff to refresh my memory. I usually recommend fellow hobbyists to start with this very good tutorial:INTRODUCTION_TO_ECG_INTERPRETATION_V8_0_July_2012
academia.edu/11339390/…tlfong01Dec 11, 11:47You might find more updated ECG materials from this Q&A site:
Medical Sciences Stack Exchange ECG
medicalsciences.stackexchange…  5 hours later… tlfong014930Dec 11, 16:56Your Lancaster Simple Element circuit design method works simple and elegant. I designed and wired the Schmitt trigger oscillator and it works without any debugging.

The triangular wave is sharp and stable, much better than that much more complicated and unstable ICL8038 and NE555 circuits.Next step is to use this triangular wave voltage to power the tunnel diode and see if I can watch the electrons swimming through the tunnel. 🙂 Many thanks for your inspiring suggestion. Ah, jogging and supper time. See you later. Cheers.  2 hours later… Circuit fantasist5702Dec 11, 18:52OK, this is a possible solution. In the Lancaster’s “elegant simplicity”, a neon lamp serves as 7414. You can see the general idea in many everyday situations. Now, you need my 90’s V-to-I module – a buffered inverting amplifier with a tunnel diode in the place of R1. I will publish a paper and post about it… also, about the “simplest IV curve tracer”…  23 hours later… tlfong014930Dec 12, 17:39I am still confused of the operation of a curve tracer (for a tunnel diode) I know the classical tracer is to show the I-V characteristic of a BJT transistor, using a scope. I think the curve tracer for a diode, including the tunnel diode, also needs a scope. The scope’s X-axis is voltage V, and Y-axis is current I.Now my very first I-V curve plotting experiment does NOT use any scope. I just vary the voltage source to the tunnel diode with a protecting, series current limiting resistor. I use a manual, two push button presses to adjust the voltage value. I use a DMM to measure the voltage across the diode, and another DMM to measure the current through the diode, and also through the resistor. After all the measurements, I use the Excel worksheet to plot the I vs V curve.The problem of using the above manual, adj PSU, and voltage and current DMM is that it is tedious to make the not too accurate DMM measurements. And it would be even more tedious to find the series/external resistance and inductance to avoid the switching/jumping over the NDR region, as described by the GE’s 1962 TD User Manual, in my BlogSpot post below.tunneldiode.blogspot.com/2020/….Ah, jogging and supper time! See you later. Cheers.  1 hour later… tlfong014930Dec 12, 19:10The pcf8951 DAC/ADC is only 8 bit resolution. So I am not sure I need higher resolution ADC, such as 10 bit MCP3008, 12 bit MCP3208, or even higher.

  2 hours later… Circuit fantasistDec 12, 21:04Okay, I’ll explain but I have to do something first and I suspect that when I’m done it will be time to go to bed there … tlfong01Dec 12, 21:20nothing urgent. You can do it in two weeks, which is what I need to sort all the ADC, DAC stuff. I just found two more old PCF8951 ADC/DAC’s in my junk box. Usually I need two or three same modules for swap testing or troubleshooting. Good night. Cheers.  5 hours later… Circuit fantasistDec 13, 2:16OK, I will comment in your blog – tunneldiode.blogspot.com/2020/….  2 hours later… Circuit fantasistDec 13, 4:22I have appended my comments in you blog also to my answer to your question in CD.  6 hours later… tlfong014930Dec 13, 9:55@Circuitfantasist Your suggestions in my tunneldiode.blogspot.com are inspiring. Let me make some quick and dirty follow up replies.Your first suggestion summarized: (1) “Let’s see what is the most important to measure the tunnel diode IV curve. IMO this is not the scope. You have to see that when increasing the voltage across the diode, the current through it decreases. …”Yes, I very much agree that the scope cannot measure the tunnel diode’s current and voltage characteristics, though it is very useful, to give a very vivid picture that the I-V curve has a mysterious gap (NDR or Twilight Zone) where the electrons. split itself into two parts, like the Schrodinger Cat, with one part jail breaking, disappearing into the Bermuda Triangle, and reappearing in the free world, …So let us forget the scope for a while and focus on how to do the I, V measurements using adj UPS, DMMs, opAmps (which I try to avoid for now, because my audiences are the U15 hobbyists in our local maker’s club) etc, …Wow, your following story is amazing: “… I think the best way to measure and plot IV curves is based on a computer. Apple II was very suitable for this purpose with its graphic features. The monitor software had a function “plot a point” that could be used by an additional program written in Assembler. In this way, in the late 80s, a few students and I created MICROLAB system, …”/ continued from above: “… The AD periphery consisted of 12-bit DAC and ADC. Later, one of these capable students, created MICROLAB BASIC – an expansion to the embedded BASIC. It consisted of a set of assembler drivers called by commands like “IN”, “OUT”, “PLOT”, etc…”So your MicroLab’s (tunnel) diode I-V plotting equipment using Apple 2 and 12-bit ADC/DAC is 20 years ahead of my 64-bit Raspberry Pi and 8-bit DAC/ADC. For our non realtime project, Rpi’s 64-bit processing is not relevant, but 12 bit resolution might be just appropriate technology, while my 8-bit PCF8951 ADC/DAC might be too weak.Your zero resistance stuff is a bit too hard for a Sunday morning reading. Anyway, it is now tea time, So see you later. Cheers. tlfong014930Dec 13, 10:53Oh my goodness, so your MicroLab I-V curve plotter is 20 years ahead of mine. I need to skip my lunch to catch up!

  1 hour later… tlfong014930Dec 13, 11:59When browsing you the links you just gave me, I suddenly remember that my original question in CD is very long, including a couple of your references, and pictures stating that origins are are from you Wikibooks. But my very long question has been condensed to CD’s standard format of 70 words, so many of my references I wish my readers/answers are removed. Anyway, I recovered part of the contents from the Cd’s history files, but the formats are incompatible to EE，tunneldiode.blogspot.com/2020/…Ｆｕｎｎｙ　ｃｈａｒ　ａｇａｉｎ，　ｎｅｅｄ　ｔｏ　ｔａｋｅ　ａ　ｂｒｅａｋ　ｔｏ　ｆｉｘ　ｔｈｅ　ｐｒｏｂｌｅｍ．  1 day later… tlfong01Dec 14, 13:24So this morning I have placed an order for the current sensor amplifier max4172:tunneldiode.blogspot.com/2020/…  1 hour later… Circuit fantasistDec 14, 14:44… instead to make it yourself? In general, this is the better solution if your goal is the element under test… tlfong014930Dec 14, 15:14I didn’t catch you. I order the 8 pin SOP chip, so I need to use the SOP 8 top DIP 8 adapter board and hand solder the SOP chip to adapter. I forgot where I placed my SOP to DIP board, so I need to order some more, in case I could not find my old ones. I will also order ICL8038 through hole chips and DIY a fixed triangle sig gen, instead of using the bigger, hard to adjust module. tlfong01Dec 14, 15:43This is the adapter board for max4172:SOP8 to DIP8 adapter board
item.taobao.com/…tlfong01Dec 14, 15:56This is the order for MCP4725:tunneldiode.blogspot.com/2020/…  1 hour later… Circuit fantasistDec 14, 17:16OK, I will look at them after my on-line meeting with my students where we are making “ideal diodes”:) See en.wikibooks.org/wiki/… and en.wikibooks.org/wiki/….  4 hours later… tlfong014930Dec 14, 21:10Ha, I watch your students doing the lab, and then more realized why I have an inferior complexity when talking to the real EE pros. I need to first introduced my background, when I studied the EE diploma in a sort of community college to be trained as a technician repairing radios in a Philips radio manufacturing factory, or American semiconductor testing plants. In short we learned more practical things, and not emphasizedon theories.So, as I often said, after the EE diploma, I still don’t know the meaning of opAmp virtual ground. I also don’t know the deeper meaning of positive and negative feedback. Also we almost only used the locally made cheap equipment for repairing radios and the more expensive equipment was always locked in the cabinets. (1) So my first surprise was seeing your students can actually hands on, touching the high class equipment which I think are for industrial grade R&D labs.So, as I often said, after the EE diploma, I still don’t know the meaning of opAmp virtual ground. You should remember that not too long ago, I mentioned that I was very grateful for the two YouTube guys D Jones and the other name I forgot, explaining the meaning of virtual ground. I never dreamed that I can “investigate” the deep practical virtual ground.(2) The other things is about dressing code. I must first mention that in those days in my city, a large proportion of people are refugees. So when I looked back, I should be dressed as a refugee in college. I still remember that I only had two cheapy coats and two jumpers which I wore for the whole winter. So I was so surprised to see your students/tutors dressed so smartly and fashionable in the lab.Of course many years later our community collage upgraded a polytechnic and had business and even fashion design departments. Well, I am not complaining, because in those years only less than 3% of those eligible to enter a university, and perhaps 5% could go to a technical college. So fast forward decades, you should see why now I am so keen to make a (tunnel) diode oscillator, playing with opamps and ADC/DAC etc.It is sort of a healing process, or repairing of my broken dream of not being able to go to America to study EE in a University. HongKong EE/ME industries did not go well after my graduation and technician years. Luckily I had other chances to study IT and software engineering and can still earn a decent living. Now the time has come to show off my software engineering knowledge and skills.For the MCP4725 12-bit ADC, I am using high class programming techniques call “Data Driven Programming” style to power the tunnel diode to hopefully force it to enter the Negative Dynamic Resistance region.Just thinking aloud, sorry for all the typo errors. Almost bed time, see you tomorrow. Cheers.  9 hours later… Circuit fantasistDec 15, 6:35Hi Fong, Again, I admire your gift for expressing yourself warmly and in such a human way. This is very rare on the web … as if people there have lost their ability to communicate naturally … Circuit fantasist5702Dec 15, 6:51Regarding the emphasis on “theories”… Maybe the reason is in me simply because I was created that way – to look for the idea and after revealing it, to explain it to others. At the same time, I am a practitioner…For example, yesterday I changed the timer of the stair lighting in the building where I live. For this purpose, I did some experiments with the buttons on the floors to find out if they are working. Also, I had to figure out the idea of ​​the timer to make sure it was damaged. Of course, these are simple but still practical skills that require some intuition and experience … especially since it is not safe … Circuit fantasistVirtual ground… It is a simple but difficult to understand concept. I myself continue to look for an even simpler explanation of this phenomenon … but in a more general form …  9 hours later… Circuit fantasist5702Dec 15, 16:24Ok, let’s try to explain it in a simple possible way: “Virtual ground” is simply a “voltage copy” of the real ground; this is the essence of the virtual ground phenomenon…So, to create such a “copy”, you simply need a voltage follower. Connect its input to the real ground and take the virtual ground from its output. The simplest voltage follower is an op-amp whose output is connected to its inverting input. Thus, the output voltage is subtracted from the input voltage at the non-inverting input… the difference is amplified many times and appears at the output… and so on so forth…This can be explained in a human-friendly manner by personalizing the op-amp. Figuratively speaking, the op-amp “compares” the voltage at the non-inverting input with the voltage of the inverting input and changes it until the former becomes equal to the latter…Read the latter as: Figuratively speaking, the op-amp “compares” the voltage at the inverting input with the voltage of the non-inverting input and changes it until the former becomes equal to the latter. Circuit fantasist5702Dec 15, 16:39From this perspective, every op-amp circuit with negative feedback contains a follower (another wisdom which cannot be found in “reputable” sources). Even the inverting amplifier contains a non-inverting follower inside – the voltage of the inverting inputs, as above, copies the voltage of the non-inverting input… and, if the latter is zero (real ground), the former will be zero as well (virtual ground)…If we put a resistor (R2) in the connection (negative feedback loop) between the output and the inverting input, the op-amp will continue keeping a zero voltage of the virtual ground…But where is the input voltage here? We include it to this following system as a “disturbance” (another wisdom). For this purpose, we connect the “disturbing” input voltage source through a resistor (R1) to the virtual ground. The op-amp reacts to this “intervention” by raising its output voltage… and we use its “reaction” as an amplified output voltage. But there is a virtual ground as before…Ohh… I have to prepare for the next meeting with my favorites. We will discuss, as yesterday, diode circuits… a very interesting topic… Nice to see you later…  3 hours later… Circuit fantasist5702Dec 15, 20:06The equipment in my lab is quite old. There is a need for modern digital oscilloscopes and functional generators. But because I am an “old war horse”, I can handle any situation…In terms of dressing, these students now have the freedom to dress as they wish. And at the time I dressed modestly. But in general, Bulgarians and especially women pay attention to their appearance … also to the home and the car … I think this is typical for small nations …  2 hours later… tlfong014930Dec 15, 21:49@Circuitfantasist Many thanks for your detailed explanation of the idea of opAmp virtual ground, using the analogy of the “voltage copy” of a real ground. I have never heard of the thing “voltage copy” so I think I need some time to digest. It would be nice if you can give a block diagram or schematic of the opAmp show the resistors R1, R2 etc. Or you can refer to one relevant chapter in you WikiBook of opAmp.Nothing urgent at all. I found that your explanation is a bit too hard for me now, because I have forgotten many of the basic concepts, and your descriptions like the following is indeed very confusing: “… Even the inverting amplifier contains a non-inverting follower inside, …” So I am reading the Wikipedia to refresh or learn new things. I need to study carefully the deeper ideas of “common mode”, “negative feedback”, “small signal transistor model”.I indeed have the feeling of first time to learn how to drive a car, or swimming, when the teacher says driving or swimming is “easy”, but to an newbie, that is a very different thing.In the mean time, I am trying to learn how to use python to import the matplotlib to plot the simple raw data of my first tunnel diode experiment. I am making a programming log in my blog, but you need to bother to understand anything for now. I will show you more when I can really plot something. The link is this:tunneldiode.blogspot.com/2020/…. Bed time now. See you tomorrow or day after tomorrow.Ah, yes, I forgot to mention that my first impression of your lab equipment such as power supplies, are desktop models, so of course more impress than my cheapy Amazon hobbyist models. However, when I read further, I found the computers in your lab are very out of date. So I agree with you that you need to upgrade some of the equipment, such as the digital oscilloscope.  7 hours later… Circuit fantasist5702Dec 16, 5:24I will try to explain the inverting amplifier in another nonconventional way (you can find millions of conventional ways on the web). The general idea of this circuit solution is to set two voltages (input VIN and output VOUT) in some proportion, e.g., VOUT/VIN = 100. Then we say that VIN is amplified 100 times (with gain of 100). VIN is an external voltage; so we have to change VOUT so that it is always 100 times higher than VIN…For this purpose, we compare the two voltages by a network of two resistors in series whose resistances R1 and R2 are in proportion R2/R1 = 100. This is a passive summing circuit with weighted inputs (1:100) that can be thought of as a kind of “electrical scales” or a “mechanical lever” (Bob Duhamel has such a movie)…In 2008, my students and I created a Wikibooks story about this “elegant simplicity”. At the end of the story, we showed how an inverting amplifier is made by this network…Let’s continue this amazing story about the legendary circuit… To compare the two voltages, we have to subtract them. So, VOUT should be with opposite polarity. Then we change VOUT until the result of the comparison (subtraction) – the voltage of the middle point between the resistors, becomes zero… and we do it continuously. This point behaves as a ground although it is not a ground; that us why it is called “virtual ground”…In the circuit of an inverting amplifier, the op-amp does this donkey work”. It “observes” the virtual ground and changes its VOUT so that to keep zero voltage at this point.As a result, VOUT/VIN = -R2/R1 = – 100.  5 hours later… tlfong014930Dec 16, 10:34Ah, your story using R1, R2 network make things a little bit clear. You remind me of Bob Duhamel’s video using a ruler with a lady. I don’t exactly understand his story. But with your story together, I am progress a little bit forward. I am very slowly reading the Wiki article on uA741 to refresh my memory on old things, at the same time relearning some new things, such the the “Hybrid T small signal model of BJT” which I did not know what is going on when the teacher talks about it, … 😦  2 hours later… tlfong014930Dec 16, 12:08Ah, your WikiBook discussion is very good in explaining your basic Voltage and Current ideas, as a background of understanding the opAmp virtual ground concept. As I said, I am refreshing my memory and relearning things I did not understand in college, when studying my rusty EE diploma, in Hongkong Technical Collage. I need some time to warm up.

  2 hours later… Circuit fantasist5702Dec 16, 13:56Here is an attractive movie about the “living voltage diagram” – photos.app.goo.gl/…… a very sophisticated experiment…And here is the explanatory text from the WB story above: “Software. Now let’s start a program that can visualize the voltage diagram on the screen as a “living” animation. For this purpose, the program make computer “interest” in the local voltages in three key points – the left resistor’s end point, the slider intermediate point and the right end point…… Let’s then satisfy its curiosity:) by connecting, for a start, the DAC1’s output to the ADC1’s input and the DAC2’s output to the ADC2’s input; then, connect the ADC3’s input to the slider. We can control the output voltages of the two DACs by the keyboard arrows; thus the two DACs act actually as programmable voltage sources…… The computer measures continuously the three voltages (VIN1, VIN2 and VIN3) and draws three voltage bars whose length is proportional to the voltage magnitudes. Finally, it connects them with a line representing the envelope of the voltage diagram.”Another but shorter movie of the screen: photos.app.goo.gl/…. Do you see any connection between this geometrical interpretation and the Bob Duhamel’s “video using a ruler with a lady”? Circuit fantasistDec 16, 14:34And something very interesting in CD – electrical.codidact.com/… where I was punished with -1 instead of being rewarded for what I reported… tlfong014930@Circuitfantasist Ah yes, the short movie is good to complement the Wikibook discussion. However, there is not subtitle in words or speech with it, so that is not very helpful, comparing with Bob Duhamel.Ah, “punished with -1 instead of being rewarded for what I reported …” is good for your mental health. Haven’t you heard this lady singing? “What Doesn’t Kill You Makes you Stronger – Kelly Clarkson 2011dec14 373,573,120 views”:
youtube.com/…. Happy listening. Cheers.  2 hours later… Circuit fantasistDec 16, 16:51Nice song…  1 hour later… tlfong01Dec 16, 18:08And one day you think you are as strong as the bounty hunter guys, you can listen “The Danish National Symphony Orchestra”:
youtube.com/…Circuit fantasistOK… Only to note the long movie is better since it shows all the possible combinations between the voltages… tlfong014930By the way, I just finished the first data conversion part of my rpi4 thonny python, declarative, newbie proof, tunnel diode I-V curve matplotlib plotting function. Will show you after my locking jog and supper. See you later. Cheers.Did I miss something? Do you mean the long WikiBook discussion with the pretty young lady? But there is no subtitle or comments, or PC programming. 🙂 Anyway, I need to go. See you late this evening or tomorrow.And if you use matplotlib, you can do animated GIF, user interactive interface. This is what I am trying to do next, plotting the tunnel diode I-V curve as animated pictures.  7 hours later… Circuit fantasist5702Dec 17, 1:43I meant my movie showing a “living voltage diagram” on the screen of Apple II… It gives a very good notion about the R1-R2 network that is widely used in op-amp circuits… BTW, in the early 90s, I was interested in TURBOPASCAL. Then I made a similar attractive experiment – “living load line”. It was implemented on the base of a data acquisition system inside an IBM PC. I have printed screenshots.  2 hours later… Circuit fantasistDec 17, 3:42Maybe, my answer would be interesting for you?  5 hours later… tlfong014930Dec 17, 8:42Do you mean your answer on Schmitt trigger? I skimmed your answer but found it too long for a morning read. Perhaps I can check it out later. I did not learn Schmitt trigger in my EE diploma, so I am interested to remedy it. So you see earlier I assembled a Schmitt trigger triangle wave gen and I will use it later for the tunnel diode experiment.@Circuitfantasist Well, I did also once use Turbo Prolog in my IBM PC days. Actually the python program I am writing now uses some of the programming ideas, such as “declarative programming style (not procedural or OO), using predicate logic etc, .. In the deleted CD chat, I remember towards the end, I told you that I will use Occam’s Razor style to answer my own question of the tunnel diode’s missing NDR plot. You see I am still working on it. 🙂BTW, I do thinkg Turbo Pascal good for small programming projects.  3 hours later… tlfong01Dec 17, 11:21About the R1 R2 notation. If you goolge opAmp images, you whould find how many images are using Rf, Rg, and Rin, and how many using R1, R2. As I often say, you are chasing your audiences away, if they don’t know your notation, and no diagrams along side to help to figure out, …  3 hours later… Circuit fantasist5702Dec 17, 14:00“Rf” is misleading since it is not only the resistor constituting the feedback network; both resistors make it (they form a voltage divider driven from the side of the output). Maybe “Rout” is more correct…I prefer to use “R1” for the input resistor (between the source and “-” input) and “R2” for the output resistor (between the op-amp output and “-” input). Of course, I always use drawings in my explanations but here it is not convenient.  2 hours later… Circuit fantasistDec 17, 16:14I am discussing now another relatedgreat idea with my students – the so-called “sense amplifier”…  6 hours later… tlfong014930Dec 17, 22:07The matplotlib is very newbie friendly. I just spent 10 minutes skimming the beginners guide, read the demo program, and only made a couple to trials and errors and successfully drew the following Tunnel Diode 2SB4B I-V Curve, using the crude manual measurements I listed in my question.

Now I am coming back to v2.0 of the tunnel diode I-V curve plotting proposal. tunneldiode.blogspot.com/2020/…. As I said earlier, this v2.0 hardware will use (1) 12-bit current sensor, (2) 12-bit ADC. Both toys arrived this afternoon, just in time to start playing. 🙂  3 hours later… Circuit fantasistDec 18, 0:48I think only Edison has worked so hard… well, me too:) Here’s my new blog post and CD.  12 hours later… tlfong014930Dec 18, 13:00I agree you can have your reason for using R1, R2 in your opAmp notation (and your “vertical bar” and “circular loop” to denote V and I).
The problem is ***consistency***: If 90% of the EE guys are using R1, R2, me newbie will definitely follow, otherwise I would not be popular among my friends, colleagues, and most importantly my students, who would have a miserable journey in their EE career. To assure easy learning curve, I strongly recommend the newbies the following tutorials: tunneldiode.blogspot.com/2020/….(see full text)  3 hours later… Circuit fantasistDec 18, 15:35You are right about R1-R2 annotation… Very useful and systematic learning scenario… I forgot to write you that I sent you an email to share something more specific …  4 hours later… Circuit fantasistDec 18, 19:20I have written some “black thoughts” in my reply to your last email:)  3 hours later… tlfong01Dec 18, 22:38Ah, I have never heard of the term “black thinking”, so I googled: healthline.com/health/….And you remind me one of the world’s 50 thinkers I admire: medium.com/@preetibhonsle/….  3 hours later… Circuit fantasistDec 19, 2:12Maybe “dark thoughts” is more correct…  9 hours later… tlfong014930Dec 19, 10:54I am not sure how to present my tunnel diode project. So I have bee browsing forums to get some ideas. I looked at Writing.CD and Writing.SE and found them good. I am particularly keen to see how other “Test Driven Developers” do. The first couple of Q&As I read are good, including these: (1) writing.codidact.com/posts/…
(2) writing.stackexchange.com/…. So I am following some of their advice in my tunnel diode test programs.(see full text)  3 hours later… tlfong014930Dec 19, 13:27So I have cone the MAX4172 current sensing amp SO8 to DIP8 adaptor soldering jog. It took me some 30 minutes.

tlfong014930Dec 19, 13:58I am planning to write the story of “How does an electron slip through a Tunnel Diode?” So I am reading more posts in Writing.StackExchange. I am very surprised to find that this Writing posts also give me a very good impression as SO did some 8 years. Example: “What is the best way to learn technical writing? Asked 8 years ago, Viewed 2k times”:
writing.stackexchange.com/…. Cheers.  2 hours later… tlfong014930Dec 19, 16:19Now I am reading MAX4172 datasheet. This reminds me why earlier I said using any answers based on opAmp is too low level. Appropriate technology is system integration of opAmp based cct.

  2 hours later… Circuit fantasist5702Dec 19, 18:38Writing was interesting for me when I was younger… Now I am mainly interested in the content and less in the form of its expression…But yesterday I was thinking about something related to this – isn’t it possible to somehow integrate text and graphics into one… let them be one thing? Because this reference from text to figure is very artificial … and the way of implementation is very different. I wonder if hieroglyphs are a more integrated way of conveying content. I don’t know, maybe you will say … This must sound very naive …In fact, I do something similar by describing a picture in words and by suggesting text in a picture …  17 hours later… tlfong014930Dec 20, 11:51Yes, your innovative idea of merging text into pictures is inspiring. One way of doing it is to hide the text behind the picture. When you click the picture, 1,000+ words would jump out explaining the picture. Below is an example showing your idea.

Now when you click the picture of the negative resistance, Wikipedia would come out explaining the “N curve”. And when you click the “superimposed I-V curve” the corresponding WikiBook would explain the colourful picture. tlfong014930Dec 20, 12:06By the way, I have been criticizing your hard to understand colourful, hand drawn, superimposing I-V curves picture. But you do inspire me to updating it to make it simple for newbies to understand. By plan is summarized below: (1) Use 4 or more MAX4172 current sense amp to measure, at the same time, four different two terminal devices (resistors, diodes etc). (2) Use one or more MPC4712 I2C built in EEPROM DAC to individually or grjoup power the diodes.(3) Use MatPlotLib to plot the superimposed colourful I-V curves, with animated images, user interaction etc.Ah, locking down lunch time! See you later.  7 hours later… Circuit fantasist5702Dec 20, 19:24Hi TL Fong,

I fell asleep today and now I’m in a hurry to go for my usual walk in the park. Just to tell you that I found some solution to the problem with my Flash movies. I made them as executable files that contain a Flash player in themselves. They are full-fledged Flash movies. I have sent to you by an imejl the first four of them dedicated to the most basic building blocks. Cheers!  9 hours later… Circuit fantasist5702Dec 21, 4:26Hi TL Fong, Today I started writing a big new and very interesting post about our chat here… Interesting thoughts are born in our conversations and I decided to extract and collect my most significant “pearls” in a post. I hope you will approve my idea.If you want, you can make a reciprocal post about your ideas. I just wonder how it is possible for a discussion with only one interlocutor to be so many times more fruitful than the many questions and answers on these sites?Your idea of mixing text and picture is very interesting. Flash provided great opportunities for such tricks and I was very fond of them.Your idea about IV curves is very interesting. As I probably mentioned, in 90s I conducted an interesting experiment where two imposed IV curves lived on the screen. I intend to write a story about this experiment that will be illustrated with printed screenshots.  2 hours later… Circuit fantasistDec 21, 6:36I have created an initial post about this chat. Later, I will structure it…  7 hours later… tlfong014930Dec 21, 13:30@Circuitfantasist I tried your executable Flash movie and found it impressive. I would give 9/10 marks on presentation style. Of course, as I said, Flash is now replaced by HTML 5. I am not suggesting you to switch to HTML5. I would think YouTube might be a good alternative. As I told you some time ago, I once tried the YouTube based MIT OCW free online course to learn EE101 and python and found it very good.Anyway, I played you Flash movie on my Chinese Win10 PC and so far so good. I would explore further later.tunneldiode.blogspot.com/2020/…  1 hour later… tlfong014930Dec 21, 14:43I watched the current loop and potential bard and found two things you might consider to improve: (1) Current magnitude is represented by thickness of the loop path. This is not very obvious. Perhaps you can make the thickness change increments bigger, or at the same time use darker colours to represent bigger current. (2) This is more misleading: the potential bar is below the resistor, NOT across the resistor, …  1 hour later… Circuit fantasist5702Dec 21, 16:07Hi Fong! First watch this video for a little fun:)Yes, the magnitudes of quantities can be coded in various manners if only there is a good attitude towards this visualization technique. But when someone writes to you that these “lines” prevent you from seeing the diagram, what do you have to do?Voltage bars are interdependent and the sum of the voltage drops across the elements in series is equal to the supply voltage (a “geometric KVL”). They do not always match the resistors, especially if the voltage drops are with a negative polarity. But this corresponds to the real situation. I had an idea to use them as an output of a simulating program… and even suggested it…  3 hours later… tlfong014930Dec 21, 19:31Ah, our chat has become TLDR and diverted too far from the original main topic of negative resistance and tunnel diode. Since you have already created a blog post for the I-Loop/V-bar graph discussion, I suggest that we CLOSE THIS CHAT ROOM, and continue our discussion in your blog. Circuit fantasistDec 21, 20:26What will happen with this chat after the closing? Will it stay here or it will be deleted?  1 hour later… tlfong014930Dec 21, 21:28Ah, don’t worry. My experience tell me that you can still visit any closed chat room. Any chat room without any activity will be frozen. Let me verify and confirm you later.Just now I visited one of my old TLDR chats a couple of months ago. It is still there. You might like to visit it to see if you can read it.(1) How to interface UART servo? (LX-224HV) Asked 3 months ago Active 2 months ago Viewed 275 times
electronics.stackexchange.com/…

(2) How to interface UART servo? (LX-224HV) Char Record
chat.stackexchange.com/rooms/…  20 hours later… Circuit fantasist5702Dec 22, 17:27I skimmed through your chats. Sophisticated techniques in the spirit of the present time … a mixture of software and hardware. I see that I have moved far away from technology and focused on the basic principles of the past … I wonder how we find a common language …I also wrote a new post about my new answer in EE. You will probably be interested to see it … there is intrigue there …I started, as you suggested, a “chat” under my post. Good idea indeed. But I think, if we decide to continue there, maybe I should find a new post in which to extract my thoughts from our comments below (the new chat)? Interesting organizational ideas …(my answer is in SE EE)1A: Emitter current

Тhe answers so far are perfect but specific; they explain how the circuit is made. For the true understanding, however, this is not enough. It is also necessary to explain why (for what purpose) this was done in this way and to consider its applications in practice. I will try to satisfy this nee…  1 day later… Circuit fantasistDec 23, 18:49If you want to know what is inside your “miracles” (a [fairy tale about CMOS](electronics.stackexchange.com/… 🙂If you want to know what is inside your “miracles” (a fairy tale about CMOS 🙂 tlfong01Ah, I am leaving this chat room and continue chatting over your new chat room for any other business.  The last message was posted 11 days ago.