New video: Basics of Tunnel Diodes

[w2aew]

This video gives an overview of the characteristics and basic applications for the Tunnel Diode.  I refer to these devices as the "bucking bronco" of the diode world - due to their wild I-V characteristic, and the fact that they'll bust into oscillation if you "look at them funny". 

[dadler]

As always, great video.

Are these diodes still used in modern products?

[w2aew]

As always, great video.

Are these diodes still used in modern products?

They may be found in some RF/microwave applications, but probably not in any kind of popular high-volume products anymore.

[dadler]

Ahh thanks. I am not familiar with them (and considered buying a few just to play with), so I searched mouser and could not find any results.

[Alex Eisenhut]

This video gives an overview of the characteristics and basic applications for the Tunnel Diode.  I refer to these devices as the "bucking bronco" of the diode world - due to their wild I-V characteristic, and the fact that they'll bust into oscillation if you "look at them funny". 

How about the unijunction transistor?

Or the diac? Makes the tunnel diode I-V curve look sedate.

[continuo]

Ahh thanks. I am not familiar with them (and considered buying a few just to play with), so I searched mouser and could not find any results.

They sure are quite expensive these days... I would have to shell out over 17 Euros to get me a single 1N3716 from a german distributor 

[mazurov]

Here's my tunnel diodes. I bought them a while back on eBay but never have time to actually do anything with them. The diodes are made of Ga-As, and specified
as 'switching type'. Units in this package have been selected at the fab for the peak current of 10 mA, about 30 years ago.



I connected one of the units to the power supply and made an
I-V graph, in 10 mV increments. It starts oscillating at 200-ish MHz past the peak, I also observed a swith to 400-ish MHz at ~0.4V. Minimum current at valley is
less than 1 mA (supply shows 0A) and my setup also stops oscillating around this point.

If anyone is curious about numbers,
the spreadsheet is available here -> https://docs.google.com/spreadsheets/d/1N-ZOeQkQ03KiGugnZ2T3KB9yKxSpm3ScF7_YWaIBdn0/edit?usp=sharing
All values are taken directly from the supply's display, previously checked against calibrated HP34401A (can't use it here, any length of wire makes big mess).
Tektronix 7104 scope, 7A24 500 MHz plugin, 7B10 time base, P6201 900 MHz 3pF FET probe, DC-coupled, ground on the center line.







The next step is to make a TD pulser described in Picosecond Pulse Labs Application Note AN-19. After Tektronix bought PSPL none of their excellent appnotes are
available from a single place; however, they can still be found on third-party sites that care,
such as this one -> http://tec.icbuy.com/uploads/2013/2/1/AN-19%EF%BC%9APicosecond_Pulse_Generation_Techniques_and_Pulser_Capabilities.pdf . It seems
that this particular diode will give me more than 0.5V step and pulse can be made up to tens of microseconds long. The terminal capacitance at valley is specified
at 10 pF, the formula on page 6 predicts 1 us rise which seems low given the frequencies at which the diode manages to oscillate - we shall see. 

[vk6zgo]

Back in the day,we used to check the transient response of our 545B with a TU-5 pulser:

http://w140.com/tek_tu-5.pdf

According to the Teknote its rise time was specified at 1.5 nS.

My employer had an in-house note showing how to use it for TDR work as well.
The 545B had a calibration output square wave which was adjustable up to 100v p-p,& this was what Tek used to drive the TU5
I had a TU5,but didn't have a source of high voltage square waves,so I gave it to a friend who had a 545B.

[mazurov]

You don't need high voltage to bias a TD; negative resistance region is below the bandgap. I was at one time considering modding a TU-5 or some other Tek pulser; Russian TDs are cheaper still and military ones are quite good.

[vk6zgo]

Yes,I know,but I didn't want to modify the TU-5.
I don't quite know why Tek designed it the way they did.

[electronican]

I had found some usefull informations about tunnel diodes:
Tunnel diode – semiconductor diode characterized by a small thickness of the pn junction, a very high concentration of dopants on both sides and a negative dynamic resistance for a certain range of polarizing voltages. It was invented in 1957 by the Japanese physicist Leo Esaki (hence sometimes it can be named Esaki diode). During research on semiconductor junctions he noticed their thus far unprecedented feature based on the tunnel phenomenon. This phenomenon causes charge carriers move through the narrow barrier layer at a very low voltage.
from here: http://911electronic.com/tunnel-diode-characteristic-symbol-definition/