diodes

Comments

• Archiver Posts: 46,084

  2001-01-24 16:59 edited 2001-01-24 16:59

  >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 Posts: 46,084

  2001-01-24 17:07 edited 2001-01-24 17:07

  >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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• Archiver Posts: 46,084

  2001-01-24 17:10 edited 2001-01-24 17:10

  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 Posts: 46,084

  2001-01-25 02:11 edited 2001-01-25 02:11

  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 Posts: 46,084

  2001-01-25 02:22 edited 2001-01-25 02:22

  how do i unsubscribe? sorry for the disturbance
• Archiver Posts: 46,084

  2001-01-25 06:18 edited 2001-01-25 06:18

  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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