Zener Diode

Discussion in 'General Electronics Chat' started by Jack Herrmann, Nov 17, 2008.

  1. Jack Herrmann

    Thread Starter New Member

    Nov 6, 2008
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    Out of a pile of diodes how do I identify a zener diode?

    Thanks in advance.

    Jack
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Usually zener diodes write on them the zener voltage. The best way is to check the part number.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Mik3's suggestion is the very best way to do it, even though it can be a lot of work.

    It's important to look at a datasheet for a Zener before putting it into use. They're tested for breakdown voltage at a specific current. If you attempt to use a Zener with it's current too far out of tolerance, you will be operating it in a non-linear region.

    All that being said, see the attached (click on the thumbnail). An LM317 regulator is used as a constant current source, supplying roughly 20mA current. This should be low enough current to avoid "zapping" most Zeners. With the input voltage being 30v, the output of the LM317 will be at most 27v when the load is high resistance.

    However, the input voltage is too high for many Schottky diodes, like the 1N5817 (20 PIV); they will be destroyed if their PIV is exceeded.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Another giveaway is the letter "B" on the end of the 1Nxxxx string.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Some have the "B" suffix, but not all; for example 1N4728A through 1N4752A.
    Often, the suffix indicates tolerance; 'A'=10%, 'B'=5%, 'C'=2%, 'D'=1% (JEDEC format)
    Other types use the suffix to indicate internal configuration; ie BAT54C = common cathode.
     
  6. bertus

    Administrator

    Apr 5, 2008
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  7. Jack Herrmann

    Thread Starter New Member

    Nov 6, 2008
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    Thanks for the information. Now I hope my eyes can read those small numbers. :)
    Jack.....KD6MRF
     
  8. mik3

    Senior Member

    Feb 4, 2008
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    There are small handy magnifiers which can help you to read these small numbers and letters.
     
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