How do you identify a diode? How to identify the diode model?

Crystal diodes are often represented by "d" plus numbers in circuits, such as: d5 represents a diode numbered 5.

1. Function: The main characteristic of the diode is unidirectional conductivity, that is, under the action of forward voltage, the on-resistance is very small; Whereas, under the action of reverse voltage, the on-resistance is very large or infinite. Because the diode has the above characteristics, it is often used in rectifier, isolation, voltage stabilization, polarity protection, coding control, frequency modulation and noise suppression circuits.

**The crystal diodes used in the machine can be divided into rectifier diodes (such as 1N4004), isolation diodes (such as 1N4148), Schottky diodes (such as BAT85), light-emitting diodes, regulator diodes, etc.

2. Identification method: the identification of the diode is very simple, the n pole (negative pole) of the low-power diode, most of the diodes are marked with a color circle on the surface of the diode, and some diodes also use diode special symbols to represent the p pole (positive pole) or n pole (negative pole), and there are also symbols marked as "p" and "n" to determine the polarity of the diode. The positive and negative poles of a light-emitting diode can be identified by the length of the pins, with the long pins being positive and the short pins being negative.

3. Test precautions: When using a digital multimeter to measure the diode, the red pen is connected to the positive pole of the diode, and the black pen is connected to the negative pole of the diode.

4. The commonly used 1N4000 series diode withstand voltage comparison is as follows:

Model 1N4001, 1N4002, 1N4003, 1N4004, 1N4005, 1N4006, 1N4007

Withstand voltage (v) 50 100 200 400 600 800 1000

Current (a) is 1A

4. Voltage regulator diode.

Zener diodes are often represented by "zd" plus numbers in circuits, such as: zd5 represents a voltage regulator with a number of 5.

1. The voltage stabilization principle of the Zener diode: The characteristic of the Zener diode is that after the breakdown, the voltage at both ends of the diode remains basically unchanged. In this way, when the regulator tube is connected to the circuit, if the voltage at each point in the circuit fluctuates due to the fluctuation of the power supply voltage or other reasons, the voltage at both ends of the load will basically remain the same.

2. Fault characteristics: The fault of the voltage regulator diode is mainly manifested in open circuit, short circuit and unstable voltage stabilization value. Of these three faults, the former one exhibits an increase in the supply voltage; The latter two faults manifest as the supply voltage drops to zero volts or the output is unstable.

The models and voltage values of commonly used voltage regulator diodes are shown in the following table

Model No.: 1N4728, 1N4729, 1N4730, 1N4732, 1N4733, 1N4734, 1N4735, 1N4744, 1N4750, 1N47511N4761

Voltage regulation: 15V, 27V, 30V, 75V

The model nomenclature of diodes is usually based on the national standard GB 249 — 74 and consists of five parts.

Part 1: Numerically representing the number of electrodes in a device.

Part 2: Representation of device materials and polarity in Chinese pinyin letters.

Part 3: Use Chinese Pinyin letters to indicate the type of device.

Part 4: Numerical representation of the device serial number.

How it worksThe crystal diode is a p-n junction formed by a p-type semiconductor and an n-type semiconductor, which forms a space charge layer on both sides of its interface and has a self-built electric field. In the absence of an applied voltage, the diffusion current caused by the difference in carrier concentration on both sides of the PN junction and the drift current caused by the self-generated electric field are equal.

Hello, I am honored to answer the diode model identification method for you as follows: there will be the name of the diode on the model remarks of the diode, and the name of the diode cavity is taken, and there are a total of five numbers and letters mixed together. 1.

There will be a 2 at the beginning, and 2 is the meaning of the diode. 2.The second number, or letter, indicates the material and polarity of the diode, 3

The third number, or letter, indicates the type of diode, 4The fourth number or letter indicates the serial number of the two lasers, 5Finally, the finch band indicates the size of the diode.

To sum up: as long as it is clear what the naming of the diode consists of, the model of the diode can be judged by the naming of the diode. <>

Here's how to measure a diode with an analog multimeter:

1. Dial the meter to the resistance rxk file.

2. Contact the front and back of the diode with two watch pens, the following situations will occur, a: one is on one side (about 2k), and the other is not on (close to infinity), which means that the diode is good. When the diode resistance is about 2 k, the side that the black pen touches is positive, and the side that the red pen touches is negative.

B: When the two watch pens are measured, the front and back sides are not passable or are both on, then the diode is bad.

3. The schematic diagram of a good diode measurement is as follows:

Schottky diodesThe differences from ordinary diodes are as follows:

1. The forward pressure drop value is different

Directly use a digital multimeter to measure (small current) ordinary diodes are above, Schottky diodes are below, ordinary diodes are left and right when high current, and Schottky diodes are below; SR350 stands for 3A50V. In addition, the withstand voltage of Schottky diodes is generally below 100V, and there is no voltage above 150V.

Second, the characteristics are different:

The most important feature of Schottky diodes is that the forward voltage drop vf is relatively small. At the same current, its forward voltage drop is much smaller. In addition, it has a short recovery time.

It also has some disadvantages: the withstand voltage is relatively low, and the leakage current is slightly larger.

Third, the pressure resistance is different:

The withstand voltage of ordinary silicon diodes can be made high, but its recovery speed is low, and it can only be used for low-frequency rectification.

If it is a high-frequency one, it will cause reverse leakage because it cannot be quickly recovered, and finally cause the tube to heat up severely.

Burnt. The withstand voltage energy of Schottky diodes is often low, but its recovery speed is fast and can be used in high-frequency occasions, so the switching power supply uses this diode as the output of the rectifier ridge hole, despite this, the temperature of the rectifier tube on the switching power supply is still very high.

Diode Characteristics:

The diode has unidirectional conductivity, and a forward voltage is added to the diode, and when the voltage value is small, the current is very small; When the voltage is exceeded, the current begins to increase exponentially, which is usually called the turning on voltage of the diode; When the voltage reaches about that, the diode is in a fully on-state, which is usually called the on-voltage of the diode, which is represented by the symbol ud.

For germanium diodes, the turn-on voltage is and the on-voltage ud is about. When the voltage value is small, the current is very small, and its current value is the reverse saturation current is.

The highest operating frequency is the upper limit frequency of the diode operation. Because the diode is connected to the p-n.

Similarly, its junction capacitance is made up of barrier capacitance. Therefore, the value of the maximum operating frequency depends mainly on the size of the p-n junction capacitance. If this value is exceeded. The unidirectional conductivity will be affected.