One Thing I Never Understood - Tunnel Diodes

Guest
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 ?
 
On Monday, December 4, 2017 at 4:44:18 PM UTC-5, jf...@my-deja.com wrote:
> http://w140.com/Ge1961TunnelDiodeManual.pdf

Thanks. I gave it a quick lookover. Saved it and will study it later.
 
On Mon, 4 Dec 2017 13:44:12 -0800 (PST), "jfeng@my-deja.com"
<jfeng@my-deja.com> wrote:

>http://w140.com/Ge1961TunnelDiodeManual.pdf

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.
 
On Monday, December 4, 2017 at 12:31:02 PM UTC-8, jurb...@gmail.com wrote:
> 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 ?

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.
 
On Mon, 04 Dec 2017 22:21:32 -0500, default <default@defaulter.net>
wrote:

On Mon, 4 Dec 2017 13:44:12 -0800 (PST), "jfeng@my-deja.com"
jfeng@my-deja.com> wrote:

http://w140.com/Ge1961TunnelDiodeManual.pdf

Are they still being manufactured?
Click to expand...

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
 
On 12/06/2017 12:22 AM, John Larkin wrote:
On Mon, 04 Dec 2017 22:21:32 -0500, default <default@defaulter.net
wrote:

On Mon, 4 Dec 2017 13:44:12 -0800 (PST), "jfeng@my-deja.com"
jfeng@my-deja.com> wrote:

http://w140.com/Ge1961TunnelDiodeManual.pdf

Are they still being manufactured?

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.
Click to expand...

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. ) :)

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

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
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
https://hobbs-eo.com
 
On Wed, 6 Dec 2017 11:14:40 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 12/06/2017 12:22 AM, John Larkin wrote:
On Mon, 04 Dec 2017 22:21:32 -0500, default <default@defaulter.net
wrote:

On Mon, 4 Dec 2017 13:44:12 -0800 (PST), "jfeng@my-deja.com"
jfeng@my-deja.com> wrote:

http://w140.com/Ge1961TunnelDiodeManual.pdf

Are they still being manufactured?

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.

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. ) :)


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

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
Click to expand...

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

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Mon, 04 Dec 2017 22:21:32 -0500, default wrote:

> Are they still being manufactured?

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.
 
On Tue, 12 Dec 2017 18:17:49 +0000 (UTC), asdf <asdf@nospam.com>
wrote:

On Mon, 04 Dec 2017 22:21:32 -0500, default wrote:

Are they still being manufactured?

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

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
 
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