Knowing the polarity of a diode is crucial for correct installation in electronic circuits, as installing it backward can prevent the circuit from functioning or even damage components. You can determine a diode's polarity primarily by visual markings on its case.
The polarity of a diode is indicated by specific markings that distinguish its positive terminal (anode) from its negative terminal (cathode). According to common practices and markings:
Understanding Diode Markings
Different types of diodes may use slightly different marking conventions. Here are the key methods based on visual cues:
Point-Contact Schottky Diodes
For small point-contact Schottky diodes, polarity is often indicated by a colored dot on the case.
- Marking: A colored dot (typically white or red).
- Indicates: The end marked with the colored dot is the positive electrode (anode).
Other Diodes (e.g., Rectifiers, Zener)
Many other types of diodes, such as standard rectifier diodes and Zener diodes, use a color band or ring around the body.
- Marking: A color ring or band.
- Indicates: The end marked with the color ring is the negative electrode (cathode).
This distinction is vital: a dot usually signifies the positive terminal for certain specialized diodes, while a band almost always signifies the negative terminal for many common diodes.
Here's a summary based on the marking types:
| Diode Type | Marking Style | Marked End Indicates | Terminal Name |
|---|---|---|---|
| Point-Contact Schottky Diodes | Colored Dot | Positive Electrode | Anode |
| Most Other Diodes (Rectifier, etc.) | Color Ring/Band | Negative Electrode | Cathode |
Always verify the specific datasheet for your diode if possible, as there can be exceptions or other less common marking methods (like symbols or notches) for certain specialized or high-power diodes. However, the dot and band methods are very prevalent.
