The cause of serious heat in the FET


In the previous article, we mentioned the characteristics of FETs, mainly including their electronic parameters, which are unipolar transistors. In this paper, we introduce the causes of serious heat generation in FETs.

There are four reasons for the severe heat of the FET:

1. The problem of circuit design is to make the MOS transistor work in a linear working state instead of in a switching state. This is also a cause of the MOS tube heating.

2, the frequency is too high, the main reason is sometimes excessive pursuit of volume, resulting in increased frequency, MOS tube loss increases, so the heat has increased;

3, did not do a good enough thermal design, the current is too high, MOS tube nominal current value, generally requires good heat dissipation to achieve. Therefore, if the ID is less than the maximum current, serious heat generation may occur, and sufficient auxiliary heat sinks may be required.

4, MOS tube selection is wrong, wrong judgment of power, MOS tube internal resistance is not fully considered, resulting in increased switching impedance.

As for the selection of MOS transistors, there are two types of enhancement type (EnhancementMOS or EMOS) and depletion type (MOS or DMOS). Each type has two types of conductivity, N-channel and P-channel. The field effect transistor has three electrodes: D (Drain) is called the drain, equivalent to the collector of the bipolar transistor; G (Gate) is called the gate, equivalent to the base of the bipolar triode; S (Source) is called The source is equivalent to the emitter of a bipolar transistor.

The selection of FETs is more important. If the selection is wrong, it is not only a serious problem of heat generation, but it is more likely that the entire circuit no longer meets the original requirements. Lujing Semiconductor offers a variety of field effect tube type models. If you need, please contact customer service online to provide you with more professional answers.


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