Unusual functions of cheap parts
 

On Sat, 26 Nov 2005 21:41:06 +0100, Winfried Salomon
wrote:

Hello Jorgen,

Jorgen Lund-Nielsen wrote:

[.....]
2N2369 for fast pulses.

btw, do you know a standard complementary pnp-transistor for the 2N2369,
such like 2N3905 but with higher ft and less feedback capacitance? It
seems that the manufactorers have almost no data on their internet pages.

mfg. Winfried

A 2N2369 is a gold-doped NPN, gold-doped to kill storage time and
improve recovery from saturation. I don't recall any PNP device with
gold-doping... or the equivalent.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Unusual functions of cheap parts
 

A metal case of a crystal should never soldered!! This may break the
oscillation characteristics. At least you must know what you're doing here.
This type of built-in failure mode is often seen in products.
Otherwise it is interesting!

Another error with crystals is to ultrasonic the populated pcb. With the
right sonic frequency the crystals comes in resonance - cracking of parts or
wires!

- Henry


"RST Engineering" schrieb im Newsbeitrag
...
Take a crystal for which you need a constant temperature. Solder the
cathode of a cheap diode (1N4148 etc.) to the crystal case. Solder one
end
of a moderately low value half-watt resistor to the case. Bring out the
anode of the diode, the free end of the resistor, and the crystal case on
wire leads and encapsulate the crystal-diode-resistor in heat shrink. Use
the diode as your temperature sensor, the resistor as your heating
element,
an opamp/driver transistor as the comparator/amplifier and bingo, the
world's cheapest crystal oven. Bang-bang or linear, your choice.

Jim



eh Henry Kiefer wrote:
Hi all -


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

Best regards -
Henry

Unusual functions of cheap parts
 

As a youngster I played with TTL DIP-ICs in my chamber and my parents next
room felt that the tv was going crazy. The pins had long wires...

- Henry

schrieb im Newsbeitrag
oups.com...
As an addition to the various mentions of common diodes as varactors
there is a well publicized British design for a frequency tripler that
will put out 2 watts at 1.3 GHz and uses five 1N914's in parallel.

I once built an HF transceiver that used CMOS logic chips for all
functions except an audio low noise amp and a voltage regulator...with
further thought those two could likely be done with CMOS logic too.

Unusual functions of cheap parts
 

The 4007 is the classic crystal oscillator circuit.
Don't forget the temperature characteristics!

- Henry

"Murray" schrieb im Newsbeitrag
...
Frithiof Andreas Jensen wrote:

"Henry Kiefer" skrev i en meddelelse
...


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


Unbuffered logic gates can make a really bad but still useful analogue
amplifier by adding feedback and bias.


E.G the CMOS 4007. See the old handbooks for a '100dB
amplifier' based on a RCA chip - there was a wiring
error in that old description - IIRC it was 3800? -
whatever, the 4007 is the same chip.

Murray vk4aok

Unusual functions of cheap parts
 

That is not new to me but thanks!
Is the oscillator useful at 150MegHz? Modulable? Maybe I can make
transmitter...
Tell us more, please.

cu -
Henry


"wa2mze(spamless)" schrieb im Newsbeitrag
. ..
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


Take one P channel Jfet and one N channel Jfet and connect them
in series so the two sources are together, connect the gate of
each transistor to the other one's drain. This is known as a lambda
connection, and if you plot the voltage vs current from drain to drain
you will see a negative resistance region, usually around 3v
(depending on the transistors). The circuit will work as a tunnel
diode oscillator up to 100-200mhz.

Unusual functions of cheap parts
 

Don't forget the LED as an low-noise zener diode with integrated function
control. Some high-fidelity enthusiasts use this in good audio amplifiers.

- Henry

"ehsjr" schrieb im Newsbeitrag
news:R3thf.9922$BU2.983@trndny01...
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

Unusual functions of cheap parts
 

There even exists LED specially taylored to the needs of doing duplex
operation.

- Henry


"Frithiof Andreas Jensen"
schrieb im Newsbeitrag ...

"Henry Kiefer" wrote in message
...

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

LED's work both ways, as a light emitter and a photodiode.

The inbuilt colour filter can be used to distinguish between Grass and Not
grass f.ex. by comparing output from a red and a green LED using white
light
as illumination.

Back when fiber was ex$$$pensive one often saw clever circuitry using two
transmitters to form a duplex connection over a single fiber.

The USD 10 solar powered garden lamps will, with a little persuation,
yield
a nice solar cell well below the price of a similar unit in the shops -
and - two 600 mAh NiMh batteries and a grotty circuit for switching the
LED.

Unusual functions of cheap parts
 

Bob Pease of National Semi mentioned a ONE AND ONLY transistor circuit
above/under voltage rail converter (with detailed theory). I cannot remember
the details. But interesting if sometime a slightly voltage behind the power
rail is needed. For example to power a CMOS Opamp now doing rail-input.

- Henry

Unusual functions of cheap parts
 

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
wrote:


"Henry Kiefer" wrote in message
...

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

LED's work both ways, as a light emitter and a photodiode.


And optocouplers can do interesting things:

Very simple high-voltage opamp, up to 400 volts p-p.

Isolated totem-pole driver, from a few volts up to 400.

Current limiter.

Low-leakage diode, sort of like an LED painted black.

John

Unusual functions of cheap parts
 

In article ,
Henry Kiefer wrote:
Don't forget the LED as an low-noise zener diode with integrated function
control. Some high-fidelity enthusiasts use this in good audio amplifiers.

It also works for this:
Vcc
!/c
--/\/\/\---+------!
! !\e
V !
--- ----/\/\/--+--- too load
! !
--------------------

You get a current limit and an indicator light.


--
--
forging knowledge