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In the past I have seen two different symbols for a zener diode. One shows the complete "Z" shape on the cathode, and one shows more of an "L" shape on the cathode (see images below):

enter image description here

What is the difference between these? Do they actually have different meanings, or are they two ways of showing the same thing? Perhaps one is European and one is American? I always thought that they were simply two ways of showing the same thing, but a coworker of mine questioned it and now I am looking for confirmation.

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    \$\begingroup\$ wikipedia has yet a different symbol, a sort of slopey Z. The lower 'Z' symbol has a danger of being confused with a Schottky diode symbol, which the top 'L' one cannot. \$\endgroup\$ – Neil_UK Jan 18 '17 at 14:34
  • \$\begingroup\$ Why just pick on the poor zener - there are lots of components with multiple symbols - they tend to be legacy items from different times and places or even particular 'house' styles. \$\endgroup\$ – JIm Dearden Jan 18 '17 at 14:49
  • \$\begingroup\$ I have never seen the upper one until now. The cathode mark on the Zener symbol should have a 'Z' appearance and the mark on the Schottky symbol should have an 'S' appearance. According to me. \$\endgroup\$ – mkeith Jan 18 '17 at 18:54
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The base symbol I can fine no definite standard reference for. I'd guess the majority of us would use it.

schematic

simulate this circuit – Schematic created using CircuitLab

Graphical samples for the Australian Standard AS 1102 (1989) Graphical symbols for electrotechnical does appear to reference this symbol. I don't have a copy, so I cannot confirm this.

Europe: International Electrotechnical Commission IEC60617 (2012) Graphical Symbols for Diagrams provide the following:

Zener Diode - IEC60617

with the IEC60617 (1996) version defining the bars. Diode Bars for:

  • Schottky
  • Tunnel
  • Zener
  • Bi-directional
  • Unitunnel

Their usage of straight bars (05-02-04) is for Bi-directional or breakdown diode.

Bi-directional or breakdown diode

US: IEEE 315 (1975) Standard for Graphic Symbols for Electrical and Electronics Diagrams provides the straight bar symbol:

Zener - IEEE 315

ANSI Y32.2 (1975) Graphic Symbols for Electrical and Electronics Diagrams has been superseded by IEEE315. It references the same symbol as IEEE315.

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  • \$\begingroup\$ Hmm, thought I'd accepted this answer a long time ago. Your chart showing the different symbols with the different descriptions was very helpful. I am accepting that the first symbol in my question is for a unidirectional zener diode and the second symbol is for a bidirectional zener, such as a bidirectional TVS diode. \$\endgroup\$ – DerStrom8 Apr 8 '18 at 12:34
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There are no differences in meaning of two symbols you showed.
Here is another of Zener diode symbol:
Zener diode

Most of electronic engineers would recognize all of them in a correct way (I mean - as Zener Diode).
Additionally there will be some reference (Voltage/part name/number) to make schematic clear.

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    \$\begingroup\$ I am aware of and familiar with the different symbols, and like I said I generally treat them the same, but I am trying to determine if there is a reason certain symbols are used instead of others \$\endgroup\$ – DerStrom8 Jan 18 '17 at 15:13

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