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

nsaspook

Joined Aug 27, 2009
7,298
Sounds like a rose with a different name... perhaps its a little bit like the difference between a zener and a transil or TVS
The two devices have completely different physics as the physical mechanism for negative resistance that limit the usefulness of each in certain types of applications. A Gunn device is not a junction diode, it's a bulk effect device the doesn't have the same storage time delays of PN junctions and has a large mass Gunn effect substrate that allows for much higher power devices than tunnel diodes.
 

nsaspook

Joined Aug 27, 2009
7,298

Wolframore

Joined Jan 21, 2019
1,748
That's the thing, negative resistance is a characteristic that can be intrinsic to device operation or it can be a dynamic effect caused by a system of components like the Four-Layer Diode using transistors.

http://www.rfcafe.com/references/electronics-world/transistors-negative-resistance-electronics-world-june-1969.htm
Good find, that is really cool and now that I’ve read it it makes perfect sense. Not sure how good of a replacement this is but there’s the ability to tune it.
 
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Thread Starter

Comrade Pingu

Joined Aug 30, 2018
20
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
So, I built the circuit as shown in the picture below.


I ran a few waveforms through it, and while it definitely modified sine and triangle waves, square/pulse waves were curiously unaffected.
The following few pictures are all from the oscilloscope measuring the voltage on the 10k resistor.





Edit: Forgot the square wave picture.

Soon, I'll make a second one of these circuits, place a capacitor between them, and see what happens.
 

MrChips

Joined Oct 2, 2009
21,134
So what you have is a clipping circuit.
Sine waves get clipped to become square waves.
Square waves are already square. You cannot make it more square.
 
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