How to judge the positive and negative poles of diodes

We all know the diode, but how do we judge its positive and negative poles? We use semiconductor diodes in almost all electronic circuits. The use of semiconductor diodes in circuits can protect the circuit and extend the life of the circuit. The development of semiconductor diodes has made integrated circuits more optimized and played a positive role in various fields. Diodes play many roles in integrated circuits and maintain the normal operation of integrated circuits.

Judging the positive and negative poles of diodes is basic knowledge of diodes, but beginners do not know how to identify the positive and negative poles of diodes. The reason is that there are different types of diodes on the market. Regarding the judgment of the positive and negative poles of the diode, this article takes the crystal diode as an example. Through this article, I hope you can learn to judge the positive and negative poles of crystal diodes.

A diode is an electronic device made of semiconductor materials (silicon, selenium, germanium, etc.). It has unidirectional conductivity, that is, when a forward voltage is applied to the anode and cathode of the diode, the diode conducts. When a reverse voltage is applied to the anode and cathode, the diode is turned off. Therefore, the turning on and off of the diode is equivalent to the turning on and off of the switch. Diodes are one of the earliest semiconductor devices and are used in a wide range of applications.

The diode is composed of a PN junction plus corresponding electrode leads and a tube package. Using different doping processes, P-type semiconductors and N-type semiconductors are made on the same semiconductor (usually silicon or germanium) substrate through diffusion, and a space charge region called a PN junction is formed at their interface. The electrode drawn from the P area is called the anode, and the electrode drawn from the N area is called the cathode. Because of the unidirectional conductivity of the PN junction, when the diode is turned on, the current direction flows from the anode through the inside of the tube to the cathode.

The diode has two electrodes. The electrode drawn from the P area is the positive electrode, also called the anode; the electrode drawn from the N area is the negative electrode, also called the cathode. The direction of the triangular arrow indicates the direction of forward current, and the text symbol of the diode is represented by VD.

There are many types of diodes, and the methods of distinguishing the positive and negative poles are also different. The following editor lists several methods for judging the positive and negative poles of diodes, for reference only.

There are many types of diodes: according to materials, there are germanium diodes, silicon diodes, gallium arsenide diodes, etc.; according to the production process, they can be divided into surface contact diodes and point contact diodes; according to different uses, they can be divided into rectifier diodes, detection diodes, Zener diodes, varactor diodes, photodiodes, light-emitting diodes, switching diodes, fast recovery diodes, etc.; according to the connection type, they can be divided into semiconductor junction diodes, metal-semiconductor contact diodes, etc.; according to the packaging form, they can be divided into Conventional package diodes, special package diodes, etc.

1. The colored end of an ordinary diode marks the negative pole.

2. The long leg of the light-emitting diode is positive, and the short leg is negative. If the legs are the same length, the larger dot inside the LED is the negative pole and the smaller dot is the positive pole. Some light-emitting diodes have a small plane, and a lead close to the small plane is the negative electrode.

You can also use a multimeter to measure the positive and negative poles. Connect the red test lead to "+" and the black test lead to "-". Use the gear RX10K to measure. The two test leads are in contact with the two poles of the diode. If the resistance value displayed is a small resistance value, then the pole in contact with the black test lead is the positive pole. On the contrary, it is negative.

3. How to identify the positive and negative poles of the Zener diode:

1. From the appearance point of view, the positive end of the metal package Zener diode body is flat and the negative end is semicircular.

2. One end with the color mark printed on the plastic Zener diode body is the negative pole, and the other end is the positive pole.

3. For zener diodes with unclear markings, you can also use a multimeter to determine the polarity. Turn the multimeter to the diode measurement range, place the two test leads on both ends of the diode, switch the two ends and test again. When you hear the buzzer of the multimeter, When the buzzer beeps, the end where the red test lead is in contact is positive, and the end where the black test lead is in contact is negative.

4. Determine the positive and negative poles of the rectifier diode in the circuit:

1. The characteristics of the diode are forward conduction and reverse blocking. Both ends of the LED are connected to the positive and negative electrodes of the battery. If it lights up, it means that the positive electrode of the battery is the positive electrode of the LED. If it does not light up, it means that the positive electrode of the battery is connected to the negative electrode of the LED.

2. The direction of current in a DC circuit is from a high potential point to a low potential point. Simply put, it flows from the positive terminal of the battery to the negative terminal of the battery through the circuit.

5. Crystal Diode

A crystal diode consists of a PN junction, two electrode leads and a tube case. It is packaged with wires on both sides of the PN junction, which is a crystal diode. The letter symbol of the crystal diode is V. The conduction direction of the PN junction is from P-type semiconductor to N-type semiconductor, that is, P to N conduction (P is the positive electrode, N is the negative electrode). The PN junction is forward-conducting and reverse-conducting, and has the characteristics of single-phase conduction.

6. The method of determining the direction of the diode through silk printing on the PCB is summarized as follows:

usually:

1. The end with the notch is the negative electrode; 2. The end with the horizontal bar is the negative electrode; 3. The end with the white parallel bars is the negative electrode; 4. The end in the direction of the triangle arrow is the negative electrode; 5. The small round end of the plug-in diode silk screen is the negative electrode. The big circle is the positive pole. 6. The first pin of the square hole of the plug-in light-emitting diode is the positive electrode.

There are many types of diodes, and the methods for judging these diodes compiled by the editor are only a small part of them. I hope it can help you who are new to diodes. The above is how to judge the positive and negative poles of diodes, which will be helpful to those who are new to circuits.