On Thu, 24 Nov 2005 18:30:06 +0100, Jorgen Lund-Nielsen
wrote:

Henry Kiefer wrote:
Hi all -

After my first thread going from "standard" cheap parts for up to vhf
frequency to a discussion about the usefulness of Spice simulator...... I
try it another time hopefully get attention of frustrated co-readers:

For example the rechtifier diode 1N4007 can be used as a rf switching diode,
for example as rx/tx-switch. This is because it is a pin structure diode.
This type is cheap and you can get it almost everywhere. It shows good
performance for the price. Surely for high-end you should do it with another
type tuned to the application it is made for. But anyway it works in some
circuits.

Do you know of other interesting devices or circuits good for misuse?

Best regards -
Henry

Tuner Switching Diodes like the european BA244 (NOT PIN-Diodes!) work
well as medium fast Step Recovery Diodes.


Tell me about it. I tried some pins to see if they would snap, and
they turn out to have incredibly mushy reverse recovery, Slop Recovery
Diodes.

I'll have to try the varicaps.

John

John Larkin wrote:

A 1N4007 can also be used as a drift step-recovery diode and as a
plasma avalanche diode. Together, two can generate a kilovolt edge
with a 100 ps risetime.

Okay, so I'm intrigued already. I have all the hardware available--two
1N4007s and a 3 kV adjustable power supply! How do I build one?

Cheers,

Phil Hobbs

On Thu, 24 Nov 2005 09:40:27 +0100, "Henry Kiefer"
wrote:

Hi all -

After my first thread going from "standard" cheap parts for up to vhf
frequency to a discussion about the usefulness of Spice simulator...... I
try it another time hopefully get attention of frustrated co-readers:

For example the rechtifier diode 1N4007 can be used as a rf switching diode,
for example as rx/tx-switch. This is because it is a pin structure diode.
This type is cheap and you can get it almost everywhere. It shows good
performance for the price. Surely for high-end you should do it with another
type tuned to the application it is made for. But anyway it works in some
circuits.

Do you know of other interesting devices or circuits good for misuse?

Best regards -
Henry

1n4007 as varactor (freq multiplier) and also Varicap.
You already mentioned RX/TX swich.
Also in PIN attenuator circuits.

Glass cased rectifiers (1n4007 in glass rather than epoxy)
as photodiode.

1n914 as 2ghz multipler (as varactor) to 100mw output.

1n914/4148 as silicon temperature sensor. (forward bias)

Base emitter of NPN silicon transistors as Zeners (5-8Vrange).
Makes a decent noise diode that way too.

Base collector of NPN si transistor as Varicap

Collector emitter of silicon transistors reverse biased as negative
resistance device.

Open GE and SI transistors are sensitive photodetectors.

Opened SCRs as photoswitches.


Allison

On Thu, 24 Nov 2005 14:47:37 -0500, Phil Hobbs
wrote:

John Larkin wrote:

A 1N4007 can also be used as a drift step-recovery diode and as a
plasma avalanche diode. Together, two can generate a kilovolt edge
with a 100 ps risetime.

Okay, so I'm intrigued already. I have all the hardware available--two
1N4007s and a 3 kV adjustable power supply! How do I build one?

Cheers,

Phil Hobbs

Google "Grekhov diode." A lot of the papers are for members only, but
this one gives the general idea:

http://www.ece.jhu.edu/~pps/ECE777/A...ano-pulse1.pdf

Grekhov discovered both the DSRD and the plasma avalanche effects in
cheap power diodes. The core of the DSRD effect is that, if a PIN
diode is forward biased for not too many nanoseconds, the carriers
don't have time to float all around the place so the charge profile is
good for a nice reverse snap. HP did the same thing in their classic
1430 12-GHz sampling head, circa 1965 roughly.

This box used the DSRD effect, in a semiconductor that one would not
expect to be used in an application like this...

http://www.highlandtechnology.com/DSS/T220DS.html

We bias the snap diode +48 volts (yes, forward direction) for about 80
ns before we turn the drive around for the snap. It was originally
designed for use in a LEAP atom probe.

John

Hi,

2N3055: one-time trigger diode with abt. 160v triggering voltage
[had some ones of unknown state left from a PSU that blew one of 5
transistors, replaced them with MJ15003]

various, sometimes expensive components: firecrackers, smoke bombs,
lamps (most of the time unintended )

old EPROMs: Lamp.Find some pins with low resistance and apply .5-2A.

the IC/transistor that was broken and took you some hours to find the
trouble:
Get 1-5 large caps (like 12 000µF 350V), charge them, and apply the
voltage to the part with a very large relay.
LOUD!

Zener diodes work fine as varicaps, at least at HF. The lower the zener
voltage and higher the power dissipation rating, the higher the C. As
someone else mentioned, transistor emitter-base junctions can be used as
either zeners (typical zener voltage around 5 volts) or varicaps.

A zener can be used as a broadband noise source. I've had the best luck
with zeners of 10 - 15 volt breakdown, with around 100 uA current. Some
are noisier than others, and they often have a critical current where
the noise is the greatest.

Tektronix used selected transistors to generate high voltage (~100
volts) fast steps (~100 ps rise time if I recall correctly) by
avalanching the collector. Some fraction of some common transistor types
worked satisfactorily in this application.

1N914 type diodes can be used as step recovery diodes to generate a step
with about a ns risetime -- maybe faster with a chip component and some
care. This could be the basis of a broadband harmonic generator.

Roy Lewallen, W7EL

) writes:

1n4007 as varactor (freq multiplier) and also Varicap.
That's not really a new thing, or specific to the 1N4007.

Sam Harris, in that first article about parametric amplifiers in
CQ circa 1958, goes into detail of what's required, and then
practically leaves the issue of the varactor to the end. At
the time, they were new, likely expensive, and not easy to get.
Sam had it easy, he worked at Microwave Associates at the time.
So then towards the end of the article where he attends to the
issue of the varactor, he basically says use whatever's available,
try things, and at least practice with those other devices until
you get good at it, at which point it's time for the "real thing".
I have quoted that bit in the past, but I don't know where I've
put the article to get the exact wording.

And ever since then, influenced by his words or maybe independent
thought, the magazines have been full of mention of using whatever's
available as a varactor, the results varying with the diode (or
junction, since some have used part of a transistor) and of course
the application.

And of course, there was one article where the author mentioned a lot
of hum in his six meter synthesizer that used something like a 1N914
for the varactor. He then realizes that the problem was the light
of a nearby lamp getting to the actual diode theough the glass
case of the diode, and hence modulating the VCO that way.

Michael VE2BVW

Take apart a couple of D cell carbon-zinc batteries.

Wash off the carbon rods. Put each in a wooden clothes pin and connect the
attached ends to the mains voltage (US customers only, please).

Tap the free ends of the rods together. Move them apart as necessary. Very
bright! Much brighter than you are.

Jon

Henry Kiefer wrote:
Hi all -

After my first thread going from "standard" cheap parts for up to vhf
frequency to a discussion about the usefulness of Spice simulator...... I
try it another time hopefully get attention of frustrated co-readers:

For example the rechtifier diode 1N4007 can be used as a rf switching diode,
for example as rx/tx-switch. This is because it is a pin structure diode.
This type is cheap and you can get it almost everywhere. It shows good
performance for the price. Surely for high-end you should do it with another
type tuned to the application it is made for. But anyway it works in some
circuits.

Do you know of other interesting devices or circuits good for misuse?

Best regards -
Henry



An LED as a shunt regulator. Also, as a varicap.
Ed

"ehsjr" bravely wrote to "All" (25 Nov 05 00:40:17)
--- on the heady topic of " Unusual functions of cheap parts"

eh From: ehsjr
eh rec.radio.amateur.homebrew:89241 sci.electronics.components:102765
eh sci.electronics.design:525790

eh Henry Kiefer wrote:
Hi all -

After my first thread going from "standard" cheap parts for up to vhf
frequency to a discussion about the usefulness of Spice simulator...... I
try it another time hopefully get attention of frustrated co-readers:

For example the rechtifier diode 1N4007 can be used as a rf switching diode,
for example as rx/tx-switch. This is because it is a pin structure diode.
This type is cheap and you can get it almost everywhere. It shows good
performance for the price. Surely for high-end you should do it with another
type tuned to the application it is made for. But anyway it works in some
circuits.

Do you know of other interesting devices or circuits good for misuse?

Best regards -
Henry

eh An LED as a shunt regulator. Also, as a varicap.
eh Ed


A TL431 precision bandgap voltage reference IC as a 400mW output
phono amplifier. It's in the application notes!

A*s*i*m*o*v

.... Marketing success has little to do with technical merit.