diodes

Archiver

Stampers,

Are there such things as "current-limiting" diodes?


Thanks in advance,

David Fixemer

Archiver

>Are there such things as "current-limiting" diodes?



Hi David,
Yes, but they are really JFETs (junction field effect transistors)
with the gate connected to the source. The 1N5283 series has
currents available from 0,2 to 5 ma. The voltage across the "diode"
has to be above 1.5 volts (and less than ~100 volts!) in order to
achieve the constant current effect. You can roll your own, using a
JFET and optionally a resistor to trim the current.

-- Tracy Allen
http://www.emesystems.com

Archiver

>Are there such things as "current-limiting" diodes?

I only know of the variety where max forward current rating is exceeded.
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David,

Yes. They're also called current regulating diodes or constant current
diodes, but they're not widely distributed. The internal construction is
actually a FET with gate tied to source, if memory serves correctly. Here's
a manufacturer link:


http://www.centralsemi.com/cld/index.html


>Are there such things as "current-limiting" diodes?

Mike Hardwick, for Decade Engineering -- <http://www.decadenet.com>
Manufacturer of the famous BOB-II Serial Video Text Display Module!

Archiver

yes there are


CMLHM080

also look in the mouser electronics catalog and they have some ....

:-)
LaQuida


>===== Original Message From basicstamps@egroups.com =====
>>Are there such things as "current-limiting" diodes?
>
>I only know of the variety where max forward current rating is exceeded.
>_________________________________________________________________
>Get your FREE download of MSN Explorer at http://explorer.msn.com

Archiver

how do i unsubscribe? sorry for the disturbance

Archiver

One of the simplest most useful current regulating
circuits I know is to take an LM317 regulator and
put a resistor from output pin to adjust pin - take
current output from the adjust pin; Vin goes to
input pin [noparse][[/noparse]shunt with .1uf to ground]. The
current out is ~ 1.25/R since the regulator has a
1.25 volt reference internally. Go to National
Semiconductor site and look at LM317 data sheet.

Regulation occurs from about 3.5 to 35 volts -
dissipation on the 317 must be respected and at
higher currents a heat sink is required.

Low end current is limited by the adjust terminal
control current - high current about 1 amp.

I recently saw some current dioded being advertised
to over 700 volts if high voltage is your requirement.

[noparse][[/noparse]I'd have to search ads to find manufacturer].

LM317s come in different packages and max current
ratings; all are cheap...

have fun... premena
>>
Date: Wed, 24 Jan 2001 08:59:15 -0800
From: Tracy Allen <tracy@e...>

>Are there such things as "current-limiting" diodes?

Hi David,
Yes, but they are really JFETs (junction field effect transistors)
with the gate connected to the source. The 1N5283 series has
currents available from 0,2 to 5 ma. The voltage across the "diode"
has to be above 1.5 volts (and less than ~100 volts!) in order to
achieve the constant current effect. You can roll your own, using a
JFET and optionally a resistor to trim the current.
<<

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