How to Tell Which Way Round a Diode Should Be
Understand how a diode functions., Learn what the diode schematic symbol means., Look for the large band., Identify the positive end of an LED.
Step-by-Step Guide
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Step 1: Understand how a diode functions.
A diode is composed of an N-type semiconductor joined with a P-type semiconductor.
The N-type semiconductor is the negative end of the diode, and is called the "cathode".
The P-type semiconductor is the positive end of the diode, and is called the "anode".
If the positive side of a voltage source is connected to the positive end of the diode (the anode), and the negative side is connected to the negative end of the diode (the cathode), the diode will conduct current.
If the diode is reversed, the current is blocked (up to a limit). -
Step 2: Learn what the diode schematic symbol means.
Diodes are indicated on schematics by a symbol (—▷|—) that shows how the diode should be installed.
An arrow points at a vertical bar, which has a line continuing out of it.The arrow indicates the positive side of the diode, while the vertical bar indicates the negative side.
You can think of it as the positive side flowing into the negative side, with the arrow indicating the direction of the flow. , If the diode doesn't have the schematic symbol printed on it, look for the ring, band, or line printed on the diode.
Most diodes will have a large colored band printed near the negative side (cathode) of the diode.
The band will go all the way around the diode. , An LED is a light-emitting diode, and you can usually tell which side is positive by examining the legs.
The longer leg is the positive, anode pin.If the pins have been trimmed, examine the the outer casing of the LED.
The pin nearest to the flat edge is the negative, cathode pin. -
Step 3: Look for the large band.
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Step 4: Identify the positive end of an LED.
Detailed Guide
A diode is composed of an N-type semiconductor joined with a P-type semiconductor.
The N-type semiconductor is the negative end of the diode, and is called the "cathode".
The P-type semiconductor is the positive end of the diode, and is called the "anode".
If the positive side of a voltage source is connected to the positive end of the diode (the anode), and the negative side is connected to the negative end of the diode (the cathode), the diode will conduct current.
If the diode is reversed, the current is blocked (up to a limit).
Diodes are indicated on schematics by a symbol (—▷|—) that shows how the diode should be installed.
An arrow points at a vertical bar, which has a line continuing out of it.The arrow indicates the positive side of the diode, while the vertical bar indicates the negative side.
You can think of it as the positive side flowing into the negative side, with the arrow indicating the direction of the flow. , If the diode doesn't have the schematic symbol printed on it, look for the ring, band, or line printed on the diode.
Most diodes will have a large colored band printed near the negative side (cathode) of the diode.
The band will go all the way around the diode. , An LED is a light-emitting diode, and you can usually tell which side is positive by examining the legs.
The longer leg is the positive, anode pin.If the pins have been trimmed, examine the the outer casing of the LED.
The pin nearest to the flat edge is the negative, cathode pin.
About the Author
Peter Fox
Specializes in breaking down complex lifestyle topics into simple steps.
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