Is there anywhere to buy tunnel diodes? + A tunnel diode distortion prototype.

Thread Starter

Comrade Pingu

Joined Aug 30, 2018
11
I've designed an audio distortion circuit using tunnel diodes (or at least have one in the prototyping phase), and I managed to use the Falstad simulator to play around with different kinds of diodes. I found out about tunneling diodes earlier today, and I wanted to use them because, well, they're quantum-y! According to the textbook on here, they're a bit rare, and pretty expensive. But, I don't want to have to go through the hassle of making lambda diodes out of p-, and n-channel FETs—especially since lambda diodes operate at higher voltages than tunneling diodes—though I'll kinda have to settle for them if tunneling diodes are pretty much relics. But, if there's some company out there that still makes tunneling diodes, does anyone know where to get them?

Tunneling diode distortion circuit

A schematic of the circuit can be seen below.


Playing around with Falstad's simulator online, I stuck the two tunneling didoes into the circuit like that. I found out that they would do some pretty weird distortions to the signal inputted, causing a bunch of what I can describe as small square waves; which isn't a surprise seeing the characteristic curve—but knowing practically nothing about it, I was really impressed with how it made an input waveform look. I also found out that the amount of distortion and the amplitude were basically linked to the RC value of the circuit. The common-emitter amp is there just to boost the output signal once it's gone through the tunneling diodes, since they can also cause the signal to lose amplitude. (Tunneling diodes act pretty weird in general—which is great for making some experimental audio effects.)

Obviously, there's still a lot of design work left to be done. I need to actually design the amplifier, then figure out what C1 value I want to use. However, I'm generally happy with how it is so far. Criticism is welcome on the circuit though.

A sketch of what the input/output waveforms looked like can be seen below. I forgot to screencap them when I played around with the circuit sim.
 

panic mode

Joined Oct 10, 2011
1,788
are you sure about that? that circuit makes no sense, what is supposed to power diodes? Vin is shorted to ground. and that is one weird potentiometer symbol
 

nsaspook

Joined Aug 27, 2009
6,285
I'm thinking it adjust the signal to be in the negative resistance curve of the diode(s) to distort the audio signal. A reversed biased tunnel diode acts like a resistor.

You can buy old US devices on ebay but they are not cheap. Russian devices are cheaper on Amazon.
 

Thread Starter

Comrade Pingu

Joined Aug 30, 2018
11
are you sure about that? that circuit makes no sense, what is supposed to power diodes? Vin is shorted to ground. and that is one weird potentiometer symbol
I hastily drew it, and all the resistors are following IEC rather than ANSI symbols. The diodes are powered by the supply; tunnel diodes aren't really good for rectification (plus diodes don't need a power input like a transistor does). Vin should probably be in the diode distortion portion of the circuit, rather than connected to it.
 

TeeKay6

Joined Apr 20, 2019
394
I've designed an audio distortion circuit using tunnel diodes (or at least have one in the prototyping phase), and I managed to use the Falstad simulator to play around with different kinds of diodes. I found out about tunneling diodes earlier today, and I wanted to use them because, well, they're quantum-y! According to the textbook on here, they're a bit rare, and pretty expensive. But, I don't want to have to go through the hassle of making lambda diodes out of p-, and n-channel FETs—especially since lambda diodes operate at higher voltages than tunneling diodes—though I'll kinda have to settle for them if tunneling diodes are pretty much relics. But, if there's some company out there that still makes tunneling diodes, does anyone know where to get them?

Tunneling diode distortion circuit

A schematic of the circuit can be seen below.


Playing around with Falstad's simulator online, I stuck the two tunneling didoes into the circuit like that. I found out that they would do some pretty weird distortions to the signal inputted, causing a bunch of what I can describe as small square waves; which isn't a surprise seeing the characteristic curve—but knowing practically nothing about it, I was really impressed with how it made an input waveform look. I also found out that the amount of distortion and the amplitude were basically linked to the RC value of the circuit. The common-emitter amp is there just to boost the output signal once it's gone through the tunneling diodes, since they can also cause the signal to lose amplitude. (Tunneling diodes act pretty weird in general—which is great for making some experimental audio effects.)

Obviously, there's still a lot of design work left to be done. I need to actually design the amplifier, then figure out what C1 value I want to use. However, I'm generally happy with how it is so far. Criticism is welcome on the circuit though.

A sketch of what the input/output waveforms looked like can be seen below. I forgot to screencap them when I played around with the circuit sim.
@Comrade Pingu
In the USA, ebay.com has many listed.
 

Alec_t

Joined Sep 17, 2013
10,384
If you can't get hold of tunnel diodes, I've been having a play on LTspice and found that an output signal similar to that shown by Bordodynov in post #9 can be obtained by use of a pair of NPNs (or PNPs) cross-coupled :-
Distort.png
 
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Thread Starter

Comrade Pingu

Joined Aug 30, 2018
11
If you can't get hold of tunnel diodes, I've been having a play on LTspice and found that an output signal similar to that shown by Bordodynov in post #9 can be obtained by use of a pair of NPNs (or PNPs) cross-coupled :-
View attachment 186973
I used the circuit in partsim (I'm at school right now so I can't use LTSpice), and I got the same result as this. However, using multisim-live, I got a radically different result:—
upload_2019-9-27_12-39-8.png

I think I'll need to build this circuit to see what's up with it. I'll be able to get my results on here in a few hours.
 

MrChips

Joined Oct 2, 2009
19,280
A tunnel diode behaves like a resistor below a certain threshold voltage.
Once the threshold voltage is exceeded (usually characterised as a threshold current) the tunnel diode exhibits a negative resistance. At this point strange things happen in any given circuit.

As such, tunnel diodes have been used as switching devices to be used in trigger circuits such as pulse detectors.
 

nsaspook

Joined Aug 27, 2009
6,285
A tunnel diode behaves like a resistor below a certain threshold voltage.
Once the threshold voltage is exceeded (usually characterised as a threshold current) the tunnel diode exhibits a negative resistance. At this point strange things happen in any given circuit.

As such, tunnel diodes have been used as switching devices to be used in trigger circuits such as pulse detectors.
One of the first RF 'bugs' I made was constructed using a Esaki Diode for the TV UHF band on an old tube set. While reading about this strange device I first became aware of another strange thing called quantum mechanics.
https://en.wikipedia.org/wiki/Leo_Esaki
https://nanohub.org/resources/4983/download/qm004.pdf
 

MrChips

Joined Oct 2, 2009
19,280
Tunnel diodes are used in the trigger section of the Tektronix 422 oscilloscope.
They are also used in nuclear pulse detection circuits such as Canberra, ORTEC, EG&G instrumentation.
 

nsaspook

Joined Aug 27, 2009
6,285
Tunnel diodes are used in the trigger section of the Tektronix 422 oscilloscope.
They are also used in nuclear pulse detection circuits such as Canberra, ORTEC, EG&G instrumentation.
This is because of very short response time (in something like a bistable trigger) of the negative resistance to external potentials. It's a extremely thin layer (speed of light across 10 nm) quantum effect, not an electron or hole mobility effect on the PN junction.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660024677.pdf

You can use a neon bulb as a negative resistance device too but the physical cause of that negative resistance is mechanically much slower.
https://en.wikipedia.org/wiki/Pearson–Anson_effect
 
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Wolframore

Joined Jan 21, 2019
1,280
They're good for use in microwave circuits for oscillators and amplification. They're used in the military due to tolerance to magentism, temp and radioactivity. Otherwise it's pretty rare which mean pricey.
 
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