Chinese Germanium 1N34

M. Hamed wrote:

> So first, here is what mine look like:
> 
> http://cfnewsads.thomasnet.com/images/cmsimage/image/automation-electronics/zener-diode-sample.JPG

** Well, they are cleary zener diodes - like the link says. 

The chip is trapped between two headers to carry heat away.

Small silicon diodes like the 1N4148 look similar. 

It sure ain't no point contact type. 



....  Phil 

On Friday, February 13, 2015 at 12:07:17 AM UTC-5, whit3rd wrote:
> On Thursday, February 12, 2015 at 12:11:21 PM UTC-8, George Herold wrote:
> 
> > > > OK for fun I did the I-V of a 1N34.
> >> > >
> > > > https://www.dropbox.com/s/gyolf6cj5cd8erw/1N34.BMP?dl=0
> > > >
> > > > I thought Germanium were supposed to be "more ideal" than Si diodes.
> > > > But the point contact thing looks nothing like the ideal diode model.
> > > > (log/ linear plot)
> 
> > The point contact is just weird.  Here's a plot of the same data
> > but log-log.
> > 
> > https://www.dropbox.com/s/5irzzrpshuqgqfk/1N34-B.BMP?dl=0
> 
> That's normal.   The so-called 'ideal diode equation' is Shockley's model
> for a planar diode (i.e. the depletion region is constant area, variable thickness),
> but a point=contact diode has a depletion region  which is a hemisphere around
> the point of contact (area proportional to R squared).

Ahh OK so as I forward bias it the area of the depletion region changes.  
(Does it get smaller with forward bias..? Just thinking out loud, I'd guess
it gets larger in area with a reverse bias.)   

Looking at my rather sketchy data, the slope at low bias is ~1 
(in a power law) and ~2.5 or so at higher bias voltages... 
with the crossover point near 30 mV or so... Near the thermal voltage.
(I have no idea if that is significant or not.)  

I could only find I-V of reversed biased Ge on a quick web search.  

https://circle.ubc.ca/bitstream/handle/2429/40864/UBC_1957_A6_7%20B8%20S8.pdf?sequence=1
 
(I like research done before I was born. :^)

George H.
> 
> The Ge point contact diodes worked well, because the low bandgap
> made impurities relatively benign (and that contact point has to be
> at the semiconductor surface, which is always dirty).   Capacitance was
> low, and gigahertz operation was easy.   Silicon point contact isn't as
> reliable because there's more dirt sensitivity, and the higher forward
> voltage means a surface electric field (attracts more dirt).
> 
> Shottky diodes for RF are not point-contact types.
> Are ANY point-contact diodes still in production?

On Thursday, February 12, 2015 at 11:19:36 PM UTC-7, Phil Allison wrote:
> 
> ** Well, they are cleary zener diodes - like the link says. 
> 

Have you ever seen low forward voltage zener diodes? That would be new to me. The forward drop on these are about .2V-.3V

M. Hamed wrote:

 Phil Allison wrote:
> > 
> > ** Well, they are cleary zener diodes - like the link says. 
> > 
> 
> Have you ever seen low forward voltage zener diodes? That would be new to me. The forward drop on these are about .2V-.3V


** But the pic IS of some Philips zeners - it damn we says so. 

http://cfnewsads.thomasnet.com/images/cmsimage/image/automation-electronics/zener-diode-sample.JPG

Piss off fool. 



.... Phil 

On Fri, 13 Feb 2015, M. Hamed wrote:

> On Thursday, February 12, 2015 at 11:19:36 PM UTC-7, Phil Allison wrote:
>>
>> ** Well, they are cleary zener diodes - like the link says.
>>
>
> Have you ever seen low forward voltage zener diodes? That would be new to me. The forward drop on these are about .2V-.3V
>
A zener by definition is reverse biased.

Using diodes as voltage regulators is not uncommon.  Just put a bunch in 
series to get the desired voltage from the individual voltage drops, and 
then feed that with a resistor.  But it's not a "zener effect".

Germanium diodes can be used the same way, but their forward voltage drop 
is lower, so unless the desired voltage is low, you'd need more.  And the 
termperature response is different from silicon, and that may be a factor.

It's not uncommon to use a forward biased silicon diode as the sensor in a 
digital thermometer, the characterstic is well known.  I can't remember if 
germanium diodes were used that way, but if so, the response would be 
different.

But this factors in when forward biasing diodes for better low level 
response, such as detecting low RF voltages.  Once you bias the diode, the 
will react to temperature, so you need another diode similarly biased but 
with no RF applied to it, to balance out the temperature response.

   Michael

Michael Black wrote:

>
> A zener by definition is reverse biased.


** But in practice may be either.

Back to back zeners are very commonly used for anti-static protection plus for AC voltage limiting and clamping in all kinds of analogue circuitry.



...  Phil 

>"During WWII, we (US and Brits) were using silicon, germanium, and 
>gallium arsenide point-contact diodes as mixers up to 30 GHz."

Huh ? 

In article <096d6805-58d6-4320-9de6-039a850a4377@googlegroups.com>, 
mhdpublic@gmail.com says...
> 
> On Thursday, February 12, 2015 at 11:19:36 PM UTC-7, Phil Allison wrote:
> > 
> > ** Well, they are cleary zener diodes - like the link says. 
> > 
> 
> Have you ever seen low forward voltage zener diodes? That would be new to me. The forward drop on these are about .2V-.3V

sure I have, after they get hammered a few times! :)

Jamie

On 2/13/2015 8:49 PM, Michael Black wrote:
> On Fri, 13 Feb 2015, M. Hamed wrote:
>
>> On Thursday, February 12, 2015 at 11:19:36 PM UTC-7, Phil Allison wrote:
>>>
>>> ** Well, they are cleary zener diodes - like the link says.
>>>
>>
>> Have you ever seen low forward voltage zener diodes? That would be new
>> to me. The forward drop on these are about .2V-.3V
>>
> A zener by definition is reverse biased.

What happens if you forward bias one?  Thought ceases to exist? Or does 
it just disappear in a flash of logic?

I'll have to try it. ;)

Cheers

Phil Hobbs


-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

On Friday, February 13, 2015 at 6:16:58 PM UTC-7, Phil Allison wrote:
> 
> ** But the pic IS of some Philips zeners - it damn we says so. 
> 

That's why I said "Looks like" not "exactly absolutely identical"

> Piss off fool. 
> 

Have you been bullied as a child? You know there is therapy for that, right?