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


Joined Aug 27, 2009
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.


Joined Aug 27, 2009


Joined Jan 21, 2019
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.
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
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.


Joined Oct 2, 2009
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.