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Author Topic: Zener Diode question  (Read 1243 times)
K1TAZ
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Posts: 15




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« on: September 29, 2017, 07:24:18 PM »

Good Afternoon,

I am a bit confused with the terminology used in connection with the Zener Diode referenced in the link below.  According to the document, the standard polarity is "Anode to Case”. Reverse polarity is also available, "Cathode to Case".  I am not exactly sure what they mean by this.  Does "Anode to Case" mean the forward bias current flow is from the anode to the case, meaning from the tab on the right side of the illustration to the case?  Or does it mean the anode of the zener diode is in the case (left side of the figure). 

For my application I want the  zener diode mounted on the PCB in contact with the ground plane, and the tab connected to the positive side of the power supply.  If I understand zener diode geometry correctly, the tab would be the cathode.  So, would this be “Anode to Case” or “Cathode to case”?

Link to illustration:  http://www.farnell.com/datasheets/222384.pdf?_ga=2.38014819.1165167698.1506713005-1724290927.1506536397&_gac=1.245630256.1506713005.EAIaIQobChMIgfCLpo_L1gIVgbjACh3wUApWEAQYAiABEgKLhvD_BwE

Thanks!
Jeff
K1TAZ




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AF6LJ
Member

Posts: 365




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« Reply #1 on: September 29, 2017, 08:18:31 PM »

Anode to case means the anode is physically connected to the mental case and the cathode is connected to the protruding lug.

The normal configuration allows for the grounding of the anode where a positive voltage is to be regulated.
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Take Care
Sue,
AF6LJ
AC5UP
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Posts: 4413




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« Reply #2 on: September 30, 2017, 12:18:19 AM »

... the anode is physically connected to the mental case

Who Knew ?
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K1TAZ
Member

Posts: 15




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« Reply #3 on: September 30, 2017, 06:24:54 AM »

Thanks, Sue!

I appreciate the help!

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