Diode Terminals - Anode, Cathode, Positive, Negative


Hey, in this article we are going to learn about diode terminals. We know that diode is a semiconductor device that allows the flow of current in one direction only while blocking the current flow to another direction. Basically, a diode is a two-terminal device. The terminals are named as either Anode and cathode or Positive and Negative. Also, remember that a diode is a polarized device so we can connect it in any polarity. For the proper operation, we need to connect it in a proper polarity or biasing.


Cathode or Negative Terminal of the Diode


Remember that through a diode current always flow from the anode to the cathode. So the cathode terminal is that through which the current leaves the diode. When the cathode terminal is connected to the negative terminal of the power source the diode will be able to conduct current and it is called forward bias. When the cathode terminal of the diode is connected to the positive terminal of the power source the diode will block the current flow and it is called reverse bias. The cathode terminal of the diode is also known as the negative terminal.


How to Identify the Cathode or Negative terminal of the Diode?


Generally, diodes have a circular line on the cathode terminal side. For example, in the 1N4001 PN junction diode(also known as rectifier diode) you will see a grey color circular line on the cathode terminal side. Same as in the 1N4148 Zener diode, you will see a black color ring mark on the cathode terminal side. In the surface-mounted or SMT diodes also you will see a mark near the cathode terminal.

Diode Terminals Identification - Anode, Cathode, Positive, Negative


Anode or Positive Terminal of the Diode


The anode terminal is that through which current enters the diode. If we want to flow the current through the diode we need to connect the positive terminal of the power source to the positive terminal of the diode. And it will be called a forward bias. But if we block the current flow by a diode then we need to connect the negative terminal of the power source to the positive terminal of the diode. It is called reverse bias. The anode terminal of the diode is known as the positive terminal.


How to Identify the Anode or Positive terminal of the Diode?


Opposite terminal to the marking side is the anode terminal. As I told you before the marking side is the cathode or negative terminal so the opposite will be the positive or anode terminal. On the anode side, there is no marking line available.


Identify Diode Polarity


Anode - Positive
Cathode - Negative


Now, the question is how to identify the terminals of a diode without any marking. In this case, we can use a multimeter to identify the terminals. Connect both terminals of the multimeter to the diode. Now change the mode of the multimeter to the continuity mode. 

Now, if you see the continuity symbol on the screen or hear the sound then the terminal of the diode which is connected to the positive terminal of the multimeter is the anode terminal and the terminal of the diode which is connected to the negative terminal of the multimeter is the cathode terminal.

But if you did not get any sound or symbol on the screen then reverse the connection between the multimeter and diode terminals and check again.


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Diode Terminals - Anode, Cathode, Positive, Negative Diode Terminals - Anode, Cathode, Positive, Negative Reviewed by Author on 11/02/2022 Rating: 5