Germanium Diode Data sheets

[olds...@tubes.com]

It seems the most "famous" germanium diode was the 1N34(A). Heck, I
remember that number from way back....

I googled up a data sheet for ALL germanium diodes. (Assuming they are
all listed), it seems there are about 20 of them.

The 1N60 is another common one, along with 1N270.

Anyhow, my reason for an interest in them is because I'm making up some
RF probes for my old oscilloscope and other test gear. These probes are
very simple, a cap, resistor and a diode. Making up a suitable housing
is more troublesome than the electronics within them.

I downloaded a bunch of schematics from the old Heathkits and Eico kits
and others. They are all pretty much the same, except some use the 1N34
while others use the 1N60. One of these has a slightly higher PIV (I
forget which one). Otherwise they dont seem too much different.

I am just wondering why some use 1N34 while others use 1N60? (and none
use any of the other germanium diodes). Is there any advantage or
disadvantage to either of them?

Also, why dont they use Silicon Diodes?

[Chuck]

Because germanium diodes have a lower voltage drop and are more
sensitive.

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[pf...@aol.com]

The 1N34 series is very often used in crystal radios - that should indicate the 'why' as compared to silicon diodes. It has to do with sensitivity at very low voltages.

There are silicon-based probes today, but germanium for the sensitivity is still preferred.

Peter Wieck
Melrose Park, PA

[olds...@tubes.com]

On Wed, 5 Apr 2017 11:24:08 -0700 (PDT), "pf...@aol.com" <pf...@aol.com>
wrote:

OK, that makes sense....

Is there any reason to choose 1N34 versus 1N60, or will both work
equally? Of the schematics I have, both were used.

I have to buy some either way, but they are cheap on ebay, like 10 of
them for around $2.50 so it's no big cost. I just need to determine
which one to buy. (Or the 1N270 are also quite available too).

[pf...@aol.com]

As I understand it, a 1N34(a) is a bit more rugged than a 60 and has a bit more voltage headroom before it clips (drops off) - but that in 80% of most applications, either will be fine. That is 100% second hand, and not from experience. I use the 34-series almost exclusively for this sort of thing and have at least 20 on hand at any one time, they are so cheap.

[John Robertson]

That's why there are spec sheets - you need to figure out which one fits
your application best. If it doesn't really matter then just get the
convenient one.

John :-#)#

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[mike]

1N21

[Michael Black]

The 1N34 was available to hobbyists early, probably because Rufus P.
Turner was connected to its development.

Realistically, what's being referenced is a germanium diode. The part
number was a descriptor, when you saw it you knew it was a germanium
diode, and that was really all that mattered. The number kept being used
because it had been used, and diodes with that number were available
through hobby outlets. I have no idea if they were all 1N34s, but they
would have all been germanium small signal diodes.

For the hobbyist, it didn't matter. They'd be used for "crystal radios",
field strength meters, rf probes, and maybe diodes in the detectors of
superhet receivers. It was never a fussy thing, except that they be
germanium. I guess the 1N82 was germanium, seen in UHF tuners as a mixer,
and used in such hobby projects where a high frequency diode was needed,
like crystal radios intended for the aircraft band. So I guess a lot of
UHF tuners in the old days had a germanium diode in them. I found a bunch
in the FM detectors of various FM broadcast radios, at a time when I would
have though silicon had taken over, indeed transistors in the same radios
were silicon.

> Also, why dont they use Silicon Diodes?
>

Because the germanium diode has a lower forward voltage drop.

Schottky diodes have lower forward voltage drop than silicon, though I
can't remember if it's lower than germanium. A DMM with a diode function
will easily separate them, all three diodes have a distinct voltage.

I went through a bunch of boards at one point, and uncovered a lot of
germanium diodes this way, certainly more than I expected.

Michael

[olds...@tubes.com]

Thanks for the info. 1N34 is one of those numbers I never forgot. Even
though I was pretty much out of electronics for near 40 years. Just like
tubes, I remembered certain ones, like 6L6 6V6 5U4 6SN7 12AU7 12AX7, and
the ones in the "american five" radios like 50C5 35W4 etc.
So, when someone says Germanium diode, 1N34 comes to mind first....

I guess from what you said, they were used more than I thought.

I have never used a Schottky diode, but I heard of them.

If I could view that chart I downloaded (PDF) showing all the germanium
diode numbers and characteristics, I'd see which of them had the higher
PIV (between the 34 and the 60). But my PDF reader is broken, and will
probably take a few hours to download again on dialup....
But I do think the 34 was the higher one, and if thats the case, that is
what I will buy and use. I think they are a few cents cheaper too, but
it's so small amount that it really dont matter.

[jurb...@gmail.com]

>"
Schottky diodes have lower forward voltage drop than silicon, though I
can't remember if it's lower than germanium. "

I think they go lower in forward drop, but I am not sure how they are with RF. They were used quite a bit in SMPSes but that doesn't mean you can just hook them up to an antenna and pick up WKRP in Cincinnati. But it does seem logical they could. I think the capacitance is an issue, an SMPS can punch though that no problem, a long wire antenna not so much.

Germanium has alot of problems, and one of them is temperature. They can only go to 100C whereas silicon can go to 200C. That is a whole different derating factor there, only half. So some silicon diodes are much better despite the voltage drop.

All this shit is only useful in very low level stuff. Nobody with half a brain would use a germanium diode or transistor in a modern design unless there was good reason. The last time I heard about it was Phase Linear, Bob Carver used germanium transistors in the current limiting circuit. I know because I had to deal with it a few years ago.

Also, there is a guy on here that wants to fix a bench power supply that uses germanium a transistor for current regulator. I would like to help but I am not quite sure what to do. There is a diode in the circuit which would have to be replaced, and then the circuit must be redesigned for the silicon transistor. I only saw a partial print of it, ad really though I can get the current limiting and whatever working, it would not be calibrated. Germanium is funny stuff. I is much different to what I am used to these days.

[Allodoxaphobia]

And, then there was the 1N21 -- a germaniun diode built in a form factor
to facilitate its use in microwave tubing. Handled a lot of them
maontaining the MG-10 radar system on the USAF F-102 Fighter Interceptor
in the 1960's.

Jonesy
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[Ralph Mowery]

In article <esaaecdp68ndml99t...@4ax.com>,
olds...@tubes.com says...

Go with the 1n34A as it has about 3 times the voltage break down as the
1n60. Somewhere around 75 volts insted of 25 volts.

The germanium has a junction voltage of about .3 volts and the silicon
.7 volts. Better sensitivity at low voltages.

[isw]

In article <et7aec1rp5ld0augk...@4ax.com>,

(Mumble) years ago, I needed some germanium diodes for an amplifier I
was designing (it was the conduction drop over temperature I
specifically needed, for thermal compensation). Found some 1N34s in a
catalog, and ordered a few. Which didn't work.

Took a while, but I finally got data sheets and (by that time) was not
very surprised to find specs of 0.7V forward drop and tempco matching
silicon, not germanium.

So in answer to your question, I'd say some of them do.

Isaac

[olds...@tubes.com]

Sounds good to me!

[Phil Allison]

Ralph Mowery wrote:

>
>
> Go with the 1n34A as it has about 3 times the voltage break down as the
> 1n60. Somewhere around 75 volts insted of 25 volts.
>
> The germanium has a junction voltage of about .3 volts and the silicon
> .7 volts. Better sensitivity at low voltages.
>
>

** FYI:

AAZ15 Ge 0.11V @ 50uA

BAT46 Schottky 0.15V @ 50uA

1N4148 Si 0.45V @ 50uA

MBR745 Schottky 0.12V @ 50uA.


That last diode is rated at 7.5A, the other are all small signal types.


.... Phil