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# tunnel diode

tlfong014886
Mon 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.

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