Diode selection plays a vital role in circuit design

On the basis of selecting the diode type, it is necessary to select the main technical parameters of the diode so that these electrical parameters and characteristics meet the circuit requirements, and it should be noted that diodes for different purposes have stricter requirements for those parameters. These are the basis for selecting diodes. . For example, when selecting a rectifier diode, special attention should be paid to the maximum rectifier current. The current through the diode cannot exceed this value during use. And for rectifier diodes, the smaller the reverse current, the better the unidirectional conductivity of the diode.

When selecting a switching diode, the switching time is very important, which is mainly determined by the reverse recovery time parameter. When selecting, pay attention to the comparison of this parameter and choose a switching diode that better meets the requirements.

When selecting the main parameters of a diode, in addition to finding out the corresponding parameter values ​​from relevant data to meet the circuit requirements, it is best to use a multimeter and other instruments to actually test them to ensure that the selected diode parameters meet the requirements and leave a certain margin. margin.

There are many types of diodes, and the same type of diodes has different models and series, which are used for detection in electronic circuits. It is necessary to choose a detector diode, and pay attention to the differences in parameters and characteristics of different types of tubes. For rectification in a circuit, a rectifier diode must be selected, and attention must be paid to the power, operating frequency and operating voltage of the circuit. For electronic tuning in the circuit, varactor diodes and switching diodes can be used. When selecting varactor diodes, special attention should be paid to parameters such as zero-bias junction capacitance and capacitance change range, and varactor diodes with different characteristics should be selected according to different frequency coverage ranges. When selecting switching diodes in electronic tuning circuits, as long as the maximum reverse operating voltage is higher than the switching voltage of the electronic tuner and the maximum average rectified current is greater than the operating current; the reverse recovery time requirements are not strict. Voltage stabilizing circuits such as power supply voltage stabilization must use voltage stabilizing diodes, and pay attention to the selection of the voltage stabilizing value. In addition, in some special circuits, light-emitting diodes, photodiodes, magnetic diodes, etc. must be used.

According to the requirements of the circuit and the size of the electronic equipment, select the shape, size and packaging form of the diode.

Diodes have various shapes, sizes, and packaging forms. The shapes of diodes include round, square, and sheet shapes, and the sizes include small, ultra-small, and large and medium-sized. The packaging forms include all-plastic packaging and metal shell packaging. wait. When selecting, qualified diodes can be selected based on performance requirements and usage conditions (including the size of the complete machine).

The selection for different diodes in different circuits is different.

How to choose several commonly used diodes in the circuit

1. For Zener diodes

As the name suggests, it plays the role of voltage stabilization. It is a diode that uses a high resistance before the reverse breakdown voltage reaches the critical time, and the voltage will remain unchanged as the current increases, so for the selection of diodes When considering the reverse current flowing through the voltage regulator tube, a current-limiting resistor is usually connected in series. Another factor must be considered, which is power. For example, if the maximum input voltage is 24V and the output is required to be 5V/20mA, then the voltage regulator tube can be 5.1V and the power is greater than 0.1W. You can use IN4733 or IN5231.

2. For rectifier diodes

The function of a rectifier diode is to convert alternating current into direct current. The selection parameters for this type of diode are: breakdown voltage VB, maximum average rectification current IF, maximum reverse operating voltage VR, etc. For example, for HER308, this is a fast recovery The reverse peak voltage and maximum DC voltage of the diode are both 1000V. It is characterized by fast switching efficiency and high efficiency. Therefore, the most important thing in switching power supplies is frequency. If it is used in the power frequency field, general rectifier diodes can be used, as long as they are durable. Pressure requirements are generally appropriate.