There are so many different types of diodes that many people have trouble identifying the polarity of the different diodes. The author of this article will explain in detail how to identify the polarity of different types of diodes.
What is a diode
A diode is an electronic device made of semiconductor materials (silicon, selenium, germanium, etc.). A diode has two electrodes, the positive electrode, also called the anode; the negative electrode, also called the cathode. When a forward voltage is applied between the two electrodes of the diode, the diode conducts; when a reverse voltage is applied, the diode turns off. The turning on and off of the diode is equivalent to the turning on and off of the switch.
The diode has a one-way conductive property. When it is turned on, the current direction flows from the anode through the tube to the cathode.
Diodes are one of the earliest semiconductor devices and are used in a wide range of applications. Especially in various electronic circuits, diodes and resistors, capacitors, inductors and other components are used to make reasonable connections to form circuits with different functions, which can realize AC rectification, modulation signal detection, limiting and clamping, and power supply Voltage stabilization and other functions.
Traces of diodes can be found whether in common radio circuits or in other household appliances or industrial control circuits.
Distinguish the polarity of the diode according to the mark on the appearance
Generally speaking, the appearance of the diode will have a relatively obvious mark. The following is the method for judging the appearance of the polarity of the diode.
Rectifier Diode Polarity
The rectifier diode usually has a white ring on the black casing, one end is the negative pole, and the other end is the positive pole.
Zener Diode Polarity
- From the appearance, the positive electrode of the metal-packaged Zener diode body is flat and the negative electrode is semicircular.
- The end with the color code printed on the plastic Zener diode body is the negative electrode, and the other end is the positive electrode.
Schottky Diode Polarity
- Check the symbol mark: The surface of the Schottky diode is generally marked with a symbol, the positive terminal is represented by a triangular arrow symbol**, and **the other end is the negative terminal.
- Diode Color Dots: In the case of point contact Schottky diodes, there are usually polarized colored dots (white or red), the end marked with the colored dot is positive and the other end is negative.
Photodiode Polarity
A photodiode encapsulated in a metal casing with a bump underneath the metal. The pin closest to the bump is the positive pole and the other end is the negative pole.
Diode Color Dots: One pin marked with the colored dot is the positive pole and the other is the negative pole.
The two pins of the photodiode are different, the longest pin is the positive electrode, and the short pin is the negative electrode.
Rectangular photodiodes are often marked to indicate that the direction of the first light-receiving surface is the positive electrode and the other direction is the negative electrode.
Led Diode Polarity
Light-emitting diodes are commonly used, and the positive and negative electrodes are easy to distinguish. The long pin is positive and the short pin is negative.
When the pins are the same, the very small metal in the LED tube is the positive pole, and the large piece is the negative pole.
SMD LEDs generally have a small bump to distinguish the positive and negative electrodes. Those with a special mark are the negative electrode, and those without special marks are the positive electrode.
Transient Suppression Diode Polarity
TVS diodes are divided into unidirectional and bidirectional, and bidirectional diodes have no polarity. The positive and negative poles of the unidirectional TVS tube are marked, the white or white circle is the negative pole, and the unmarked end is the positive pole. **
Looking at the model, we can judge the polarity from the surface of the model. Although different brands have different naming methods, there are rules.
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