One Thing I Never Understood - Tunnel Diodes

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Its theory of operation escapes me. I know there is a negative resistance part of its IE curve, but doesn't that just make it into a current source through that range ?

I read they can make an oscillator out of it or a UHF amp, and Tektronix used them in their trigger circuit in scopes. (those did seem to be really good triggering circuits, would lock onto anything)

Is there a place with some explanations and sample circuits with their theory of operation ?  

Re: One Thing I Never Understood - Tunnel Diodes
http://w140.com/Ge1961TunnelDiodeManual.pdf

Re: One Thing I Never Understood - Tunnel Diodes
On Monday, December 4, 2017 at 4:44:18 PM UTC-5, jf...@my-deja.com wrote:
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Thanks. I gave it a quick lookover. Saved it and will study it later.

Re: One Thing I Never Understood - Tunnel Diodes
On Mon, 4 Dec 2017 13:44:12 -0800 (PST), "jfeng@my-deja.com"

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Are they still being manufactured?

I fooled with some gunn diodes.  Built little cavity resonators out of
3/4" copper pipe caps, and had a blast setting off radar detectors.

Re: One Thing I Never Understood - Tunnel Diodes
wrote:

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Back diodes are still being manufactured, as zero-bias RF detectors.
They are low-peak-current tunnel diodes. I think back diodes are/were
the only germanium devices manufactured with a photolithograpic
process.

Somebody was still making the old GE TDs a few years back, frightfully
expensive. The fab process was insane.




--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: One Thing I Never Understood - Tunnel Diodes
On 12/06/2017 12:22 AM, John Larkin wrote:
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Ge is a pain to do litho on because its oxide is water-soluble, so it's
hard to control noise and leakage due to surface states at the
semiconductor-insulator interface. (Diamond would be just that much
worse, of course. ) :)

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And the junction capacitance was equally insane, like 200 pF.  The
really fast ones had peak currents of about 200 mA.  I have a bag full
of 1-mA ones, which aren't that interesting.  I got a dozen or so
Russian InGaAs TDs off eBay awhile back but haven't tested them yet.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: One Thing I Never Understood - Tunnel Diodes
On Wed, 6 Dec 2017 11:14:40 -0500, Phil Hobbs

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Some of the old GE and RCA parts had insane Ip/Cj ratios, enough to
give 25 ps risetimes.

This still works, last time I checked:

https://www.dropbox.com/s/goe9pjxe34zec25/TD_Pulser.JPG?raw=1

and this is the TDR step generator from an old HP sampler:

https://www.dropbox.com/s/gl6rb0fbvdysn4m/HP_TD_Pulser.JPG?raw=1

For a long time, a tunnel diode was the fastest thing around.


I have a lot of 5 mA axial GE parts. There was a bin at HalTek full of
them, 10 cents each.  


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: One Thing I Never Understood - Tunnel Diodes
On Mon, 04 Dec 2017 22:21:32 -0500, default wrote:

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I doubt so, they were expensive and had a very narrow market.

Some eastern EU users, mainly form Russia and Ukraine sell
cheap NOS USSR made germanium tunnel diodes on Ebay.
(example: https://www.ebay.com/itm/263344534127 )
Anyway they can be simulated using available components;
a search for "lambda diode" or "negistor" on google images
will bring lots of examples.
I have used the lambda diode configuration in the past and
loved it for being so simple and practical: it used no  
reactive parts other than those employed in the tuned circuit,
so that it would oscillate from audio to the UHF just by
using a different LC circuit. Making a great GDM out of
it was just a matter of adding a detector and a meter.

Re: One Thing I Never Understood - Tunnel Diodes
wrote:

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I used to design digital stuff with TDs.

My 1964 Allied catalog shows a 1N914 at $1.89, and a 1N3716 (5 mA Ip
tunnel diode) for $2.55.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: One Thing I Never Understood - Tunnel Diodes
On Monday, December 4, 2017 at 12:31:02 PM UTC-8, snipped-for-privacy@gmail.com wrote:
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Not 'current source' (that's HIGH impedance, not negative).   It makes it a gain
element (in series with a positive resistor, it makes an attenuator with AC gain according to
the formula).

Attenuation_factor =  Z_1/(Z_1 + Z_tunnel)     >1 when Z_tunnel is negative

The reason diodes don't forward-conduct until you get some voltage across 'em
is that there's an insulating 'depletion region' that gets thin when you forward-bias.
But, a bit of tunneling (Zener-style conduction) happens before the forward-bias,
ONLY if there's a no-energy-change path (the P valence and N conduction bands have to
have energy ranges that overlaps).  

Forward bias removes that overlap by shifting P versus N voltage bias, reducing the tunneling.

Leo Esaki (Nobel prize, 1973) figured it out.  Good treatment here:
<http://www.ee.sc.edu/personal/faculty/simin/ELCT563/08%20Tunnel%20Diodes.pdf

Real (normal, non-tunneling) diode conduction happens at higher
voltages.

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