Main parameters of semiconductor diodes


The physical quantity describing the characteristics of the diode is called the parameter of the diode. It is a quality indicator that reflects the electrical performance of the diode and is the main basis for the rational selection and use of the diode. In the semiconductor device manual or the manufacturer's product catalog, the various types of diodes are listed in tabular form. The main parameters of the diode are as follows:


1. Maximum average rectified current IF (AV)


IF (AV) is the maximum forward average current allowed to pass through the diode during long-term operation. It is related to the area, material and heat dissipation conditions of the PN junction. In practical applications, the operating current should be less than IF (AV), otherwise it may cause the junction temperature to be too high and burn the PN junction.


2. Highest reverse working voltage VRM


VRM is the maximum reverse voltage allowed to be applied when the diode is used in reverse. In practical applications, when the reverse voltage is increased to the breakdown voltage VBR, the diode may be damaged by breakdown. Therefore, the VRM is usually taken as (1/2 to 2/3) VBR.


3. Reverse current IR


IR is the reverse current when the diode is not reversed. Theoretically IR = IR(sat), but considering the surface leakage and other factors, the IR is actually slightly larger. The smaller the IR, the better the unidirectional conductivity of the diode. In addition, IR is closely related to temperature and should be used when using it.


4. Maximum working frequency fM


fM is the maximum frequency at which the diode is allowed to pass the AC signal during normal operation. Do not exceed this value in practical applications, otherwise the unidirectional conductivity of the diode will be significantly degraded. The size of fM is mainly determined by the capacitance effect of the diode.


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