How to discern Germanium-Diodes from Schottky-Diodes
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- Опубликовано: 28 янв 2017
- 1N60P and 1N34A "Germanium-Diodes" sold on EBay are in fact most often Schottky-diodes.
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Rogers shows an easy method how to discern Germanium-diodes from Schottky-diodes 
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I used a fake Germanium diode sold as 1N34 which in reality is a Schottky diode, it gave excellent selectivity much better than true germanium diodes OA90, OA81 and a diode with two black rings. I tested them on a magnetic loop which is based on your design but made it 12% larger. Also tested 18 SWG and 175X46AWG litz wire, satisfied with both but the later much more expensive. There is a powerful local signal which was strongly interfering with two close weak AM radio signals. With germanium diodes I was unable to stop the interference but with the fake schottky diode the problem has been solved, stations tune very sharply. There is some loss of sound quality but still satisfactory.
Thanks for the heads up!!
This is pretty good. Thanks.
If you look at the data sheet, 1N60 is Germanium (without "p"), whereas 1N60p is a Schottky with a similar forward voltage. So they didn't necessarily lie to you about the 1N60, but rather were probably confused.
Chinese vendors are cheating at every possible instance. I´ve got a dozen different components which were faked. So this is a deliberate cheap from the vendors because they explicitly advertise the diodes as "Germanium".
thanks for sharing information
Interesting. Might be worth trying to check both germanium and Schottky diodes with a curve/signature tracer, like the one featured in Mr Carlson's Lab or the one built into the Hameg HM204 scope. Anyway, I've got a good stock of vintage germanium diodes, probably the Polish AAP153. Not letting them go :)
I have some old glass-sealed Sylvania 1n54a diodes and they have a small amount of a white powder in them...any idea what that is? I tested them and they have a very slightly positive capacitance curve from 0-5v.
Promptly crack them open and snort the contents.
Schottky diodes can be as good as or better than germanium detectors in crystal sets but unless you're buying pre-tested and selected Schottky diodes, you will need to purchase a package of a few dozen or more to test and hand-pick as performance can range from weak or almost no detection to excellent performance.
Hi thanks for the great video...now since eBay are a lot of fake germanium diode would you mind where to buy the original germanium diode?
Either from Ebay if you explicily search for the AA... Germanium-diode series (clear glass body, point-contact can be seen clearly instead of the typical orange inside of a Schottky-diode)
Or the older OA.... Germanium-diode series (glass-body, painted black).
Or the AA113 from us: www.ak-modul-bus.de/stat/germanium_detektor_diode_aa113_crystal_d.html
(picture is not original but copied from the Schottky-diodes)
You can be quite sure if you buy a AA... or OA...-type that it´s not a relabeled fake.
Growing up, these things were everywhere - I started with OA81s. Nowadays, finding a real one is like finding Unicorn droppings.
the green stripe indicates germanium? i need a replacement diode for my oscilloscope. its a green stripe with 2 blue stripes
You usually can take any Germanium diode available. They only differ by the maximum current. In most cases also a cheap Schottky diode will do the work, or even a silicon diode. Depends on how the diode is used in the circuit.
@@KainkaLabs ok .one more thing I have zener diodes on hand ? I have no idea on current or voltage
@@KainkaLabs I emailed the company and they gave me the schematics its a 1ss83 diode
Do these schottky diodes work well in crystal radio set ??
Germanium diodes have a dynamic resistance of only a few kOhms. Thereby they load the tank-circuit much too much so that the voltage breaks down.
The remedy in the old days was that the voltage and (high) impedance of the tank-circuit was transformed down to match the dynamic impedance of the crystal-/germanium.diode and of the typically 2x2kOhm headphones behind them.
Disadvantage: When transforming down the reception voltage you loose weak stations because every semiconductor-material needs at least a voltage of around 25mV to rectify at room-temperaure!
(This is governed by the laws of physics and can´t be changed except by cooling down the diode down to sub-zero temperatures.)
Schottky-diodes have a much higher dynamic impedance and are matched much better to the high impedance of a tank-circuit (in resonance).
Thereby you don´t need to transform down the tank-circuit and have much a better result in receiving low-level stations.
So Schottky-diodes make a much better use of the reception-voltage of the tank-circuit.
I will explain this in great detail in a future video series which will be named "Mythbusting Crystal-Radios" or something like that.
99% of the information you find on the internet concerning crystal-radios is totally wrong.
And the first myth is that germanium diodes are better than Schottky or Silicon diodes because they have a lower "turn-on" or "knee" voltage...
read the reply; still have the same question; do the "fake" 1n34a diodes work as well or better than the "real" 1n34a point contact germanium diodes?
@@KainkaLabs You are doing good work, keep it up
do the "fake" diodes work as well?
Schottky diodes have a much larger dynamic impedance (orders of magnitude between 100kOhm...10 Megohm) and thus work much better when antennas/LC tank-circuits with a high Q-factor and thus high resonance resistance are directly coupled to the diode/crystal radio. But then of course you also have to load them only with that (high) impedance which needs a little transformer to transform the impedance of the headphones up to the dynamic impedance of the diode.In contrast true Germanium diodes only work with a coupling winding to transform the resonance resistance of the LC tank-circuit down to the dynamic impedance of the diode (only a few kOhms for Germanium).In the end Schottky diodes give a much better result because the limiting factor is the so called temperature voltage (ca. 25mV at room temperature) which has to be overcome by the signal for a diode to be a rectifier. Below the temperature voltage a diode does not rectify and is only a resistor! That is dictated by physics and cannot be overcome.If you think about that you will recognize that a Germanium diode can never be as good as a Schottky diode because the necessary coupling winding is down-transforming the signal-level so that you need a higher reception voltage in the tank-circuit to get a signal high enough to being rectified by the Germanium diode.This is a mostly unknown fact in the "community" but is well known by the "Gurus" in that field.I will make a little video-series about "Mythbusting Crystal-Radio Sets" in a few months where this topic will be adressed and the false myth about Germanium-diodes will be busted (together with other myths like the "infinite" impedance of crystal earphones etc.)Read the other comments I posted down below if you want to learn more (although a lot or repetitions...)
I'm confused now. If he Schottky diode is cheaper and has lower reverse leakage and also lower forward voltage drop than germanium diode than isn't that a good thing?
Yes, of course. Schottky diodes are far superior to Germanium diodes in any application I can think of.
@@KainkaLabs I wonder why crystal radio hobbyists seem to discount the schottky diode? I was under the impression that reverse leakage was a problem. But you seem to be saying that schottky diodes are superior to germanium diodes in that regard. I guess I need to build my own crystal radio and test it out for myself. Still it's true that Chinese and other sellers are misrepresenting schottky diodes as being authentic germanium diodes. That is dishonest and I also have been cheated.
I think I explained this in some detail in a former comment. Just take a look at the earlier comments by me.
Component tester is handy for testing. 👍
No, because the componetn tester cannot differentiate between Germanium ans Schottky diodes. They have the same forward characteristic, but usually the reverse current is not measured. And the reverse current makes the difference.
I have health challenges and the mental fog is very high, today. Please explain how to set up this test without your crystal radio unit. Can it be done with just a typical 0-30V/0-3A PSU? I have a Siglent. I also have several nice multimeters. All steps, please. Thank you.
It is just a 3V voltage source and a 10k (log.) potentiometer and the diode is in reverse mode. The multimeter in current-mode is in series with the diode and the multimeter in voltage-mode parallel to the diode. But you need a multieter with 1 Gigohm or more input impedance in voltage mode!
@@KainkaLabs My Siglent DMM is the 3065X model = 6.5 digit and "10GΩ: set the input impedances in ranges of 200 mV, 2 V and 20 V to 10GΩ, while in ranges of 200 V and 1000 V, the impedances are still 10 MΩ." So, I should be able to cover the impedance requirement. I take it that the potentiometer is set up as a voltage resister divider. If so, I can just vary the voltage (and current, as well) with the PSU; correct. Thank you, so much, for your reply and help.
"1N60P and 1N34A "Germanium-Diodes" sold on EBay are in fact most often Schottky-diodes"
I would be surprised if anyone is doing Germanium semiconductor wafer fabrication these days. Like the op says, easily visually and electrically identified. Also look for the S shaped point contact wire inside the envelope. You're stuck with vintage if you want the real thing.
There are germanium diodes with less reverse current. You can't say it's not a germanium diode unless you test the metals inside.
Do you have a datasheet for those?
In my experience the reverse current of germanium diodes and Schottky diodes (of similar max. forward-current) differs by so many orders of magnitude that you can be pretty sure to determine the type by measuring the reverse-current.
And you can -with diodes in a transparent glass body- also discern them by their look under a magnifier.
Germanium diodes are typically with a bend (gold) wire bonded to the germanium crystal while Schottky diodes have a large planar contact-zone with this typically orange colour.
@@KainkaLabs What I'm trying to say that as long as you use germanium inside it would be a "germanium diode", even if of atypical construction. For example, if you took the standard construction of a Schottky diode but replaced the silicon with germanium. These are probably fake, but it isn't a question of whether or not they contain germanium, but whether or not the characteristics match the data sheet.
And that´s the point: Schottky diodes do _not_ have the same properties/characteristics as Germanium diodes.
It´s not only the much lower reverse current of Schottkys but also the completely different dynamic/differential resistance.
E.g. in crystal radios many people still prefer genuine Germanium diodes over anything else (although the opposite is true: Schottky diodes have just because of their much _lower_ reverse current superior properties for crystal radios).
If a diode is sold as "Germanium" diode it must have Germanium as a PN-junction (in contrast to a Schottky diode which has a metal-semiconductor junction and works from a totally different physical effect) . Anything else is at least misleading if not cheating. Genuine Germanium also sell for much higher prices because they have become quite rare and are AFAIK nowhere fabricated any more.
If they would be sold as "low forward voltage" diode or as a _replacement_ type, it would be OK.
But these diodes are advertised as Germanium diodes and they are not.
KainkaLabs
Another 100% accurate method of determining if it's germanium is how sensitive the device is to changes in temperature. The leakage current of germanium is much more sensitive to temperature changes than silicon.
What angers me is that some circuits are designed with depending on the germanium diode's leakage current to function. Some detector diodes charge a DC blocking capacitor and discharge the blocking capacitor through the diode's leakage. These seem to be the problem circuits if low leakage Schottky diodes are used. It seems to me that a high value resistor to simulate the leakage would help the Schottky diode to work like the true gernamium diodes. I am speaking about detectors not used in crystal sets. The crystal sets may not work with a resistor because the resistor has a linear V-I characteristic, and the germanium doesn't.
One thing that might help is to put many of the 'fake germanium' Schottky diodes in parallel to increase the leakage current. The fake diodes are so much cheaper than real germanium that a dozen or more of them could be paralleled. Or high current Schottky diode like the 1N5817 could be used to get high leakage current.
You can check if it's a germanium diode by X-Raying it and looking at the response frequencies if you really want. Electrical characteristics wont give you a sure answer as to whether or not there is germanium inside.
You can't tell simply by electrical characteristics because there are many possible variations on the "germanium diode". Specifically reverse current leakage is a function of electron band gaps. This is not an inherent feature of germanium, but happens due to the P-N doping bands. But you could use a different dopant with different properties, having higher or lower electron energy bands without changing the germanium. Or you could connect germanium to a metal like copper and probably get a similar effect (which transition metals would work is something I haven't checked).
You might think this isn't a germanium diode, but making claims like this could get you sued by some manufacturer of a "low reverse current germanium diode".
You're making overbroad generalizations that aren't guaranteed to hold true.
빨리빨리 설명하시지,, current and drop voltage 만 빨리 보여주면됨.
Fell for the fakes. ebay is full of them. Criminal,