What is a crystal diode? What are the basic structure, principle, classification, application, identification method, detection, and selection method of a crystal diode

A crystal diode is a type of diode made from semiconductor materials, also known as a diode or transistor. It has many advantages, such as small size, light weight, strong pressure resistance, long service life, etc., so it is widely used in electronic devices.

1、 Basic structure:

Crystal diodes are composed of P-type semiconductors and N-type semiconductors. The electron concentration of P-type semiconductors is higher than the hole concentration, while the electron concentration of N-type semiconductors is higher than the hole concentration. Two semiconductors are connected through a P-N junction to form a junction capacitor. When an external voltage is applied on both sides of the junction capacitor, an electric field is formed on both sides of the junction capacitor.

2、 Working principle:

The working principle of crystal diodes is based on the characteristics of PN junctions. When the PN junction is in forward bias, that is, the P terminal is connected to a positive voltage and the N terminal is connected to a negative voltage, electrons flow from the N terminal to the P terminal, and holes flow from the P terminal to the N terminal, forming a current. When the PN junction is in reverse bias, that is, the P terminal is connected to a negative voltage and the N terminal is connected to a positive voltage, electrons and holes will be attracted by the electric field and cannot flow, forming a small reverse current.

3、 Category:

Crystal diodes are mainly divided into two categories: small signal diodes and power diodes. Small signal diodes are suitable for low current, high-frequency applications, while power diodes are suitable for high current, low-frequency applications. According to different structures, crystal diodes can also be divided into point contact diodes, surface contact diodes, alloy contact diodes, etc.

4、 Application:

Crystal diodes have a wide range of applications in electronic devices, such as:

Signal detection: Crystal diodes can be used to detect the presence and strength of signals, commonly used in devices such as radios and televisions.

Rectification: Crystal diodes can convert AC signals into DC signals, commonly used in power supply and other applications.

Protection: Crystal diodes can be used for overvoltage protection, overcurrent protection, etc. in circuits.

● Luminescence: Crystal diodes made of certain special materials can emit visible light, used for indicator lights, display screens, etc.

5、 Identification method:

1. Appearance recognition: Crystal diodes typically have a slender positive (anode) lead and a short negative (cathode) lead. The positive electrode lead is generally marked with an arrow or marked end, while the negative electrode lead is the other end. In addition, it can also be identified by features such as size, shape, and color of the appearance.

2. Component identification: Crystal diodes are usually labeled with information such as model, manufacturer, batch, etc. on the housing. You can identify it by consulting relevant information or asking the manufacturer.

3. Data manual: Detailed parameters and specifications of crystal diodes can usually be found in their data manuals. You can search for accurate information by model or manufacturer name.

6、 Testing:

1. Positive voltage measurement: Use a multimeter or digital voltmeter to connect the positive lead to the positive pole and the negative lead to the negative pole, and then measure the voltage. If the measured voltage is within the normal operating range, it indicates that the diode is functioning properly. Otherwise, there may be a malfunction.

2. Reverse voltage measurement: Using a multimeter or digital voltmeter, connect the positive lead to the negative lead and the negative lead to the positive lead, and then measure the voltage. Under normal circumstances, the voltage of a diode should be very low, close to zero. If a large voltage is measured, it indicates that the diode may have a fault.

3. Current measurement: Use an ammeter to measure the forward and reverse currents of a diode. Under normal circumstances, the forward current should be within the rated current range, while the reverse current should be very small. If the current exceeds the rated value or the reverse current is large, it indicates that the diode may have a fault.

7、 Selection method:

1. Determine application requirements: Determine the operating current, voltage, frequency, and other parameters of the diode based on specific application requirements.

2. Search for data manual: Based on application requirements, find the appropriate diode model and carefully read the relevant data manual to understand its parameters and performance.

3. Choose the appropriate packaging form: Based on the actual application environment and assembly method, choose the appropriate diode packaging form, such as pin type, surface mount, etc.

4. Brand and Quality: Choose well-known brand diodes and pay attention to quality assurance.

5. Cost considerations: Choose the appropriate diode model and brand based on budget and cost requirements.

When selecting crystal diodes, it is necessary to consider the parameters, performance, and reliability of the components. The main parameters considered include rated current, rated voltage, reverse breakdown voltage, etc; In terms of performance, factors such as switch speed, temperature characteristics, and frequency characteristics need to be considered; In terms of reliability, it is necessary to consider the voltage resistance and lifespan of the components.

Summary: Crystal diode is a commonly used electronic component with a wide range of applications. Understanding the basic structure, principles, classification, applications, identification methods, detection and selection methods of crystal diodes is an important foundational knowledge for electronic engineers and enthusiasts.