The future of germanium ? ( diodes mainly )

: Dave Moore wrote: : > I'm interested in hearing the thoughts of ye experts : > about the future of germanium. : >

: > Specifically, germanium diodes, as I have decided : > to possibly take to market some of my old circuit : > designs that used germanium diodes. : >

: > There would seem to be a number of semi-houses that : > still manufacture them, however they certainly don't seem : > to be a hot item at any of the popular distributers. : >

: > Another disturbing trend :-) is the so-called : > *improvement* in leakage specs. This may : > be an "improvement" for some applications, : > but to those in the world of guitar amplifier : > FX design, this could well be the death nell. : >

: > So what thinketh ye ? Will the good old leaky : > Ge diode soon go the way of long since deceased : > reptiles? : >

: > Thanks : > Dave Moore : >

"John Popelish" wrote in message news: snipped-for-privacy@adelphia.com...

: How do silicon Schottky diodes sound in your designs?

Terrible :-) Technically they work, but tonewise, they fail the old scientific "ear test".

They will : certainly be around for a while.

I've certainly experienced some interesting results during a few brief experiments with Schottky's and intend to delve into their sonic qualities a bit more deeply in the future. Ah, if only there were enough time in the day ( about 64hrs/day might suffice :-) : : I am waiting for someone to come up with a germanium nitride : passivated germanium transistor. Moisture sensitivity of the old : unpassivated germanium transistors was one of their worst faults.

How about the diodes? Same problem? Most of the diodes I've been using to date were scrounged from old TV and radio boards that were stored in a rather humid environment. They seem to be healthy AFAIK.

Thanks Dave Moore.

How do silicon Schottky diodes sound in your designs? They will certainly be around for a while.

I am waiting for someone to come up with a germanium nitride passivated germanium transistor. Moisture sensitivity of the old unpassivated germanium transistors was one of their worst faults.

Can't you 'soften' a Schottly diode with a small series resistor and add the leakage in reverse by adding a large resistor in parallel?

Meindert

: > : How do silicon Schottky diodes sound in your designs? : >

: >

: > Terrible :-) Technically they work, but : > tonewise, they fail the old scientific "ear test". : : Can't you 'soften' a Schottly diode with a small series resistor and add the : leakage in reverse by adding a large resistor in parallel? : : Meindert

Actually, I'm planning to attempt to get the same effects from generic silicon eventually. Wherein, I expect to encounter as with your suggestion, the same drawback, which is an increased parts count and extended development time.

For some reason that I haven't yet taken the time to understand, the schottky's introduce a rattling sound when used in some of these circuits. Whether a damping resistor will tame the abberrant carriers, dunno. Time will tell I spoze and thanks to hurricane Katrina, I have about half the time that I used to these days )`:

--DM--

: > Specifically, germanium diodes, as I have decided : > to possibly take to market some of my old circuit : > designs that used germanium diodes. : >

: > There would seem to be a number of semi-houses that : > still manufacture them, however they certainly don't seem : > to be a hot item at any of the popular distributers. : >

: > Another disturbing trend :-) is the so-called : > *improvement* in leakage specs. This may : > be an "improvement" for some applications, : > but to those in the world of guitar amplifier : > FX design, this could well be the death nell. : >

: > So what thinketh ye ? Will the good old leaky : > Ge diode soon go the way of long since deceased : > reptiles? : >

: > Thanks : > Dave Moore : >

: >

: One major "killer" go Germanium transistors was the use of Indium for : doping; it made for a rather low temperature specification. : Late in the life of "flower power" transistors, a different doping : element was used - making the power transistors *more* temperature : resistant than "sand power" transistors. : But, sand power somehow won the day. : If you need lots of low Vf diodes and do not mind them being leaky : and having crappy breakdown voltages, then use schottky diodes.

Hey, that's the best argument for schottky's I've heard yet :-)

One major "killer" go Germanium transistors was the use of Indium for doping; it made for a rather low temperature specification. Late in the life of "flower power" transistors, a different doping element was used - making the power transistors *more* temperature resistant than "sand power" transistors. But, sand power somehow won the day. If you need lots of low Vf diodes and do not mind them being leaky and having crappy breakdown voltages, then use schottky diodes.

One of my first tasks, as a Junior Engineer, at my PoE was to redesign a boatload of circuits to eliminate Germanium diodes and transistors (and schottkys were cheating). ...that was 30 years ago.

I thought the dinosaurs were already dead.

InSb makes a dandy detector for 3-5 micron IR, though. You have to cool it to 77K before it really acts like a semiconductor, though.

Perhaps Intel is going to use little bits of InSb for heterojunction transistors or something strange like that? It would make sense except I think the only bipolars that Intel makes are the parasitic ones that crop up in CMOS designs.

doping; it made for a rather low temperature specification.

Hum, I don't see how that's possible- Ge has a lower bandgap than Si, so no matter what you dope it with, electrons are going to bump through the junction by thermal energy that much easier.

I recently saw mention that Intel(?) was going to try indium antimonide. I looked up the bandgap and it's lower than Ge, as you'd imagine. I don't know what the hell they're thinking...

Tim

-- Deep Fryer: a very philosophical monk. Website:

On microchips the fastest bipolar devices currently made are SiGe, typically with fT » 35GHz.

...Jim Thompson

Maybe they're thinking of things that can do 5 GHz at about a volt Vcc. :-)

Cheers! Rich

Not too sure; i found a CK722 that is still good!

Silicons have the same nonlinear effect as Ges, but it occurs over a small V range with a large V offset added, making it much tougher to use for audio distortion than ge. Biasing them with a constant current might help, but you've got 2 diodes to bias with 2 different Vs to get symmetry. I'd stay with ge!

What production volumes are you looking at? If its only small, you may be able to get a batch of ge diodes or trs off ebay or similar.

I dont know whether youve played with copper or selenium diodes, those have similar uses, but again are even harder to find. Muggins here has a batch of miniature metal signal diodes somewhere I've never found a use for.

NT

very low voltage for power saving? Would have many uses in computers etc. Ge tr circuits can run happily on 0.5v supplies.

NT

Where do you get such misinformation?

...Jim Thompson

which bit specifically? Ge diodes dont have the Vdrop that silicons do at low v, and can be used unbiased for some apps. And are, or were.

NT

"...tougher to use for audio distortion..."

TC'ing a Si transistor with Si diodes is no tougher than TC'ing a Ge transistor with Ge diodes, EXCEPT the Ge will probably thermally run-away in spite of your efforts.

...Jim Thompson

I gues we were thinking of 2 different things then. Ges can be used back to back in an opamp circuit to give a nice nonlinear effect, with no bias. I dont know exactly what the OP's doing, thats just the usual design I've seen.

NT

wrote

: Dave Moore wrote: : : > Actually, I'm planning to attempt to get the same : > effects from generic silicon eventually. : > Wherein, I expect to encounter : > as with your suggestion, the same drawback, which is an : > increased parts count and extended development time. : >

: > For some reason that I haven't yet taken the time to : > understand, the schottky's introduce a rattling sound : > when used in some of these circuits. Whether a damping : > resistor will tame the abberrant carriers, dunno. : > Time will tell I spoze and thanks to hurricane Katrina, : > I have about half the time that I used to these days )`: : > --DM-- : : Silicons have the same nonlinear effect as Ges, but it occurs over a : small V range with a large V offset added, making it much tougher to : use for audio distortion than ge. Biasing them with a constant current : might help, but you've got 2 diodes to bias with 2 different Vs to get : symmetry. I'd stay with ge! : : What production volumes are you looking at? If its only small, you may : be able to get a batch of ge diodes or trs off ebay or similar. : : I dont know whether youve played with copper or selenium diodes, those : have similar uses, but again are even harder to find.

I have a few seleniums on hand that just for kicks I plan to play with someday, but like you said, even harder to find.

: Muggins here has : a batch of miniature metal signal diodes somewhere I've never found a : use for. : : : NT

Muggins? That would be your cat? I'll have to introduce her/him to my lab-cat Tabbitha who as of late seems determined to become a parts distributor. In fact, she distributed a bunch of my paper/oil caps all around the place just the other day :-) :