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I read in applications of tunnel diodes that it can be used as a memory element. I am not able to justify or verify this statement. It would be very helpful if a circuit showing logic storage using a tunnel diode is included in the answer.

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    \$\begingroup\$ Can you link to the article and statement that you read? Have you looked at the VI characteristic of a tunnel diode? Do you know that it has a section in the curve that has negative dynamic resistance (clue)? \$\endgroup\$
    – Andy aka
    Nov 26 '20 at 13:13
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By providing a resistive load line for a tunnel diode, the memory effect can be exploited.

As a kid, buying a tunnel diode from Lafayette Electronics, I found 100 ohm series resistors provided a STEEP enough load line that I could map out the entire I_V curve (this from memory, of decades_ago tinkering).

However, high_resistance load lines would have the SNAP between states; a coupling capacitor would inject the charge transient needed to flip between states.

I did not evaluate the state_store behavior.

I did use the Tunnel Diode as an oscillator.

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Andy: from what I recall of the I_V curve(s) for a tunnel/Esaki diode

  • a HIGH VOLTAGE and a HIGH RESISTANCE provide the snap_memory

I'd draw an I_V curve, but stackX no longer allows my browser that ability.

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  • \$\begingroup\$ The series resistance has to be low enough to cause a current significantly more than the valley current (in other words) or it won't (appear to) work. \$\endgroup\$
    – Andy aka
    Nov 26 '20 at 13:43
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    \$\begingroup\$ Back in 1969, I bought some RCA tunnel diodes along with this: RCA Tunnel Diodes for Switching and Microwave Applications, Technical Manual TD-30, ©1963. I still have all this. Pages 52-54 show how tunnel diodes can be used as computer memories. Indeed, the section starts out by stating "Because of its voltage-controlled negative-resistance characteristic, the tunnel diode is an ideal element for computer memories." Frankly, it makes no sense to me now, and didn't back then either, but I can scan the pages and post a link to the scan, if desired. \$\endgroup\$
    – Ed V
    Jan 27 at 1:02
  • \$\begingroup\$ @analogsystemsrf, I agree that "a HIGH VOLTAGE and a HIGH RESISTANCE provide the snap_memory". But why? \$\endgroup\$ Jan 27 at 13:40
  • \$\begingroup\$ @Ed V, You took me back to the distant 70s, when I, as a student at the same university where I have been teaching until now, first encountered this strange semiconductor device and circuit phenomenon. Then I did not understand it but I was deeply impressed. I managed to explain it much later, in the middle 10s, when, in a fierce "fight" with orthodox Wikipedians, I tried to explain it to Wikipedia readers. I have told it in my WP user page (Negative resistance section). Thanks for your story; it touched me deeply. \$\endgroup\$ Jan 27 at 13:58
  • \$\begingroup\$ @Circuitfantasist Thanks for your comment: it means a lot to me! I bought those first RCA tunnel diodes near the end of freshman year at RPI. I loved the idea that they worked by the quantum mechanical concept of tunneling and I wanted to make an oscillator, which I did. But I had no oscilloscope or power supplies other than batteries and my breadboard was a perf board with spring clips (from Radio Shack). Really crude, but electronics is fantastic for providing opportunities for creativity! Electronics is a wonderful mix of deep, practical, fun and challenging. \$\endgroup\$
    – Ed V
    Jan 27 at 14:48
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This is just to supplement the accepted answer by @analogsystemsrf. Since the OP specifically expressed an interest in seeing a tunnel diode circuit where the tunnel diode was the logic storage element, the next two figures are scans from my hardcopy of the RCA Tunnel Diodes for Switching and Microwave Applications, Technical Manual TD-30, ©1963 by RCA.

RCA Manual p. 42

Credit: My scan of page 42 of the reference above.

RCA Manual p. 43

Credit: My scan of page 43 of the reference above.

There is lots more in this old $1.50 technical manual!

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  • \$\begingroup\$ Ed V, Great thoughts! I remember these boards with spring clips. I have also been thinking a lot about how to make the perfect solderless board. I guess you will be interested to see how I realize my youthful circuit dreams in the lab of Semiconductor Devices and Basic Circuitry with my students... and especially the investigation of the tunnel diode IV curve with a "jump". \$\endgroup\$ Jan 27 at 18:02
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    \$\begingroup\$ Thanks for the links: great to see all that! The tunnel diode characteristic curve is magnificent! I used to teach an electronics course for undergrad and beginning chemistry grad students (I am a retired chemistry professor) and especially loved the teaching lab! Here is a temporary link (I will delete in 3 days) to a couple of my photos of my electronics, etc. The quest for the ideal solderless breadboard is something I have been on for many years, as the photos will show. It would be terrific to have that quest be successful! \$\endgroup\$
    – Ed V
    Jan 27 at 18:55
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    \$\begingroup\$ @Circuitfantasist Please see my comment directly above! In the excitement of the moment, I forgot to direct it to you! \$\endgroup\$
    – Ed V
    Jan 27 at 19:15
  • \$\begingroup\$ Ed V, Interesting devices that remind me of military equipment... Resistors sealed in glass ampoules? In the 80's I had to make a charge amplifier for a vibrometer and I remember that I put such a 1 Gohm "glass" resistor in the DC feedback. Floating battery power supplies and battery input voltage sources? I have always preferred them in laboratory experiments. Another example is a (rechargeable) [battery put into the negative feedback](loop.en.wikibooks.org/wiki/Circuit_Idea/Group_66a) to see how the op-amp will react to such a disturbance... \$\endgroup\$ Jan 27 at 21:15
  • \$\begingroup\$ ... Almost a whole computer on prototyping boards? Very flexible and suitable for experiments... I cut multimeter's probes and replace them by needles (a piece of stiff wire) to easily stick them into the holes of prototyping boards. Similarly, I replace the scope probes by stiff conductors (blue, red and black in the picture) to stick them directly into the board holes. Of course, this works well for relatively high voltages. \$\endgroup\$ Jan 27 at 21:26

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