How to Identify Simple Diodes

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Last Updated: March 10, 2025

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• By Number
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A diode is a simple electronic component which blocks current in one direction and allows it in the other. They can be manufactured to work forward or reverse, and with positive or negative voltage. Uses for a diode include, current protection, AC/DC conversion, and capture/emitting light. With so many varieties it can be difficult to determine what type a diode is.

Steps

Method 1

Method 1 of 2:

By Shape

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1. 
   1
   Look for legs on the side:

   • 1. Standard Signal - This is the regular forward-biased diode.
   • 2. Zener - Operated in reverse-biased to hold a constant voltage
   • 3. Small Signal - Used for applications with a much smaller current but with much more accuracy
2. 
   2
   Look for both legs under:

   • 1. Light Emitting Diode - Emits a colored light based on the materials used internally
   • 2. Photodiode - Captures photons to generate current
   • 3. Infra-Red - Emits light at the infra-red spectrum
   • 4. Varactor - A reverse-biased diode used as a capacitor
   • 5. Schottky - Used for precision and when voltage needs to be conserved
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3. 
   3
   Look for pins. These will be chips in the form of a SMD (surface mounted device). To identify these you will need to look at the number.
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Method 2

Method 2 of 2:

By Number

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1. 
   1
   Rotate or read the number off the surface of the diode.
2. 
   2
   Go to alldatasheet.
3. 
   3
   Type the number in the search bar.
4. 
   4
   Determine the type from the results and even get the datasheet while doing it.
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Tips

• If you cannot see number, it's best to throw it away and get a new one. Most diodes are cheap
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• If your diode does not match anything shown, try the number search.
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• If your diode is not listed on all datasheets, recheck the number to make sure you put in the correct one. Use a search engine to find other datasheet sites.
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Things You'll Need

• Diode
• Good light source (for seeing the numbers)
• Device with internet connection