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** But the pic IS of some Philips zeners - it damn we says so.
That's why I said "Looks like" not "exactly absolutely identical"
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.
So what? All standard zener diodes are used in reversed bias mode too. Go
back to basics.
The b-e junction of a transistor often makes a good zener, roughly 5
volts typically.
There are some transistors that you can use emitter to collactor as a
reference zener, which is a zener with a forward diode in series, with
a net tempco near zero. That's a lot cheaper than buying a classic
2-chip reference zener. 6.2 volts seems to be the magic number.
On Sat, 14 Feb 2015 11:49:36 +1000, Michael Black <et472@ncf.ca> 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.
Not so, and by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
"During WWII, we (US and Brits) were using silicon, germanium, and
gallium arsenide point-contact diodes as mixers up to 30 GHz."
Huh ?
Explain which part and you'll get some deeper answer.
On Mon, 9 Feb 2015, Baron wrote:
Phil Allison prodded the keyboard
Baron wrote:
** Err - try visual inspection first:
http://www.lessmiths.com/~kjsmith/crystal/s1N34A-3.jpg
They look nothing like that. But if 1N34 is a pretty generic
diode, there could be more than one manufacturer I assume.
The drop is about .2-.3V but the first datasheet I looked up,
doesn't match the parameters I'm getting.
No it doesn't look like any of my 1N34's either !
** Wot - not clear glass and no die on the end of a header or tiny
wire making a point contact?
Sure your 1N34s are genuine ?
.... Phil
Oops, Sorry Phil, Guys. A brain fart !
I've just looked at the ones I have, they are 1N23. Still in the lead
foil packets.
SO they are microwave diodes. Apparently they don't want much current
through them, one was not supposed to use a VOM to check them (so I'm not
sure if a DMM is acceptable or not).
That's the progression. In WWII, they worked on radar, improving it and
finding that they needed to move up in frequency in order to get good
enough definition. In doing so, they helped pave the way for more use of
those higher frequencies after the war. They were able to get tubes to
transmit up there (by making new types of tubes) but had problems with
tubes that operated up there. So they went to crystal diode mixers, and
went back to the "cat's whisker" of the early days, except making it more
stable, so you didn't have to fiddle to find where on the surface there
was good operation.
and it caused Bell to look at the transistor after the war. I forget the
title, but there is a book about this, something about the invention that
changed the war, which is interesting in telling the story of Radar
development during WWII, and its impact after the war.
I noticed something interesting related to the 1N34 a few years ago. I
had downloaded a 1930s copy of The Radio Handbook and one of the people
thanked at the beginning was Rufus P. Turner.
On Sun, 15 Feb 2015, David Eather wrote:
On Sat, 14 Feb 2015 11:49:36 +1000, Michael Black <et472@ncf.ca> 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.
Not so, and by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
One surplus store here used to sell "zeners", some specific voltage, and
they were plastic encased transistors with a lead cut off. They must have
gotten them that way.
Michael
On Sun, 15 Feb 2015, David Eather wrote:
On Sat, 14 Feb 2015 11:49:36 +1000, Michael Black <et472@ncf.ca> 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.
Not so, and by the way all diodes are zener diodes - we just don't
normally run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
On Sunday, February 15, 2015 at 1:10:21 PM UTC-7, David Eather wrote:
So what? All standard zener diodes are used in reversed bias mode too. Go
back to basics.
I thought someone here or elsewhere mentioned that Zener effect is not necessarily the same as the avalanche effect in regular diodes.
On Sun, 15 Feb 2015 12:39:52 -0800 (PST), "M. Hamed"
mhdpublic@gmail.com> wrote:
On Sunday, February 15, 2015 at 1:10:21 PM UTC-7, David Eather
wrote:
So what? All standard zener diodes are used in reversed bias
mode
too. Go back to basics.
I thought someone here or elsewhere mentioned that Zener
effect is
not necessarily the same as the avalanche effect in regular
diodes.
The physics is different, zener (quantum tunnelling) at low
voltages
and avalanche at high voltages, midway being around 5 volts
maybe.
Most people and data sheets call all such diodes "zeners."
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
One surplus store here used to sell "zeners", some specific voltage, and
they were plastic encased transistors with a lead cut off.
On Sunday, February 15, 2015 at 10:35:49 AM UTC-8, Michael Black wrote:
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
A word of warning: don't test the reverse bias on point-contact,
or light emitting, or low-noise photodiodes.
On Sunday, February 15, 2015 at 10:35:49 AM UTC-8, Michael Black wrote:
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
A word of warning: don't test the reverse bias on point-contact,
or light emitting, or low-noise photodiodes.
I've seen LEDs in cheap Chinese and Indian products run directlyOn Sunday, February 15, 2015 at 10:35:49 AM UTC-8, Michael
Black
wrote:
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't
normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
A word of warning: don't test the reverse bias on
point-contact,
or light emitting, or low-noise photodiodes. Those devices
have
very sensitive near-surface regions that only stay clean if the
electric field isn't given an unexpected polarity.
Like I think I said earlier, the microwave diodes out of WWII like theOn 2/17/2015 3:47 PM, whit3rd wrote:
On Sunday, February 15, 2015 at 10:35:49 AM UTC-8, Michael Black wrote:
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
A word of warning: don't test the reverse bias on point-contact,
or light emitting, or low-noise photodiodes.
_Forward_ biasing some photodiodes can lead to tears, due to horrible current
crowding at the contact. However, at least with Si, Ge, and InGaAs devices,
reverse bias causes no worries right up to the rating.
On Tue, 17 Feb 2015 12:47:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:
On Sunday, February 15, 2015 at 10:35:49 AM UTC-8, Michael Black wrote:
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
A word of warning: don't test the reverse bias on point-contact,
or light emitting, or low-noise photodiodes.
Reverse biasing photodiodes is the usual way to use them. It reduces
their capacitance and makes them a lot faster.
--
John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
whit3rd wrote:
On Sunday, February 15, 2015 at 10:35:49 AM UTC-8, Michael
Black
wrote:
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't
normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
A word of warning: don't test the reverse bias on
point-contact,
or light emitting, or low-noise photodiodes. Those devices
have
very sensitive near-surface regions that only stay clean if the
electric field isn't given an unexpected polarity.
I've seen LEDs in cheap Chinese and Indian products run directly
from 230VAC with a single series resistor and nothing else. That
obviously places the LED in reverse breakdown every half cycle. I
haven't paid enough attention to see if/how their performance
changes with time.
George Herold wrote:
On Wednesday, February 18, 2015 at 1:25:53 AM UTC-5, Pimpom
wrote:
whit3rd wrote:
A word of warning: don't test the reverse bias on
point-contact,
or light emitting, or low-noise photodiodes. Those devices
have
very sensitive near-surface regions that only stay clean if
the
electric field isn't given an unexpected polarity.
I've seen LEDs in cheap Chinese and Indian products run
directly
from 230VAC with a single series resistor and nothing else.
That
obviously places the LED in reverse breakdown every half
cycle. I
haven't paid enough attention to see if/how their performance
changes with time.
I reversed biased several LEDs.. most were good up to ~100V or
so..
230VAC seems like a lot... but maybe with the "right" led.
I see now how my post could be incorrectly interpreted. I mean a
*single* LED used as a power indicator, not a string of them, and
without any other component shunting it to prevent reverse
operation. The series resistor limits the current in both forward
and reverse breakdown mode. Usually these are run at a mA or two.
The preceding post by whit3rd made me wonder if LEDs used like
this suffer significant degradation in light ouput or lifespan.
On Wed, 18 Feb 2015 06:17:28 -0800 (PST), George Herold
gherold@teachspin.com> wrote:
On Tuesday, February 17, 2015 at 10:51:44 PM UTC-5, John Larkin wrote:
On Tue, 17 Feb 2015 12:47:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:
On Sunday, February 15, 2015 at 10:35:49 AM UTC-8, Michael Black wrote:
On Sun, 15 Feb 2015, David Eather wrote:
...by the way all diodes are zener diodes - we just don't normally
run them in the breakdown region.
Yes, all diodes can "zener" but they are reversed biased.
A word of warning: don't test the reverse bias on point-contact,
or light emitting, or low-noise photodiodes.
Reverse biasing photodiodes is the usual way to use them. It reduces
their capacitance and makes them a lot faster.
Anyone tried taking a garden variety photodiode up to the point
where it starts avalanching?
(Maybe in a dark room... there are some thing better done with the
lights off :^)
No, but that's what an APD does (probably with special doping)
--
John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com