P-channel mos tube symbol

    First, the input resistance of the MOS tube itself is very high, and the gate-source electrode capacitance is very small, so it is highly susceptible to the induction of external electromagnetic fields or static electricity and charged, and a small amount of charge can form a fairly high voltage (U=Q/C) on the electrode capacitance, which will damage the tube. Although the MOS input side has anti-static protection measures, it still needs to be treated with care. In storage and transportation, it should be packed with metal containers or conductive materials, and it should not be placed in chemical materials or chemical fiber fabrics that are easy to produce electrostatic high pressure. During assembly and commissioning, tools, meters, and workbenches should be well grounded. To prevent damage caused by static interference of the operator, for example, do not wear nylon, chemical fiber clothes, hands or tools before touching the integrated block. When the device leads are straightened or bent or manually welded, the equipment used must be well grounded.

    Second, the protection diode at the input end of the MOS circuit, the current tolerance is generally 1mA when it is switched on. When there may be too large transient input current (more than 10mA), the input protection resistance should be connected in series. The 129# was not included in the initial design of the protective resistance, so this is also the reason for the possible breakdown of the MOS tube, and by replacing a MOS tube with an internal protective resistance should be able to prevent this failure. Because the instantaneous energy absorbed by the protection circuit is limited, too large instantaneous signals and too high electrostatic voltage will make the protection circuit lose its function. Therefore, the soldering iron must be reliably grounded during welding to prevent leakage and breakdown of the input end of the device. In general use, the waste heat of the soldering iron can be used for welding after power failure, and the grounding pin must be welded first.

    The basic physical characteristics of static electricity are: there is an attractive or repulsive force; There is electric field, potential difference with the earth; A discharge current is generated. These three conditions can have the following effects on electronic components:

    1. The component absorbs dust, changes the impedance between the lines, and affects the function and life of the component.

    2. The insulation layer and conductor of the component are damaged by electric field or current, so that the component cannot work (complete damage).

    3. Due to instantaneous electric field soft breakdown or current overheating, the element is injured, although it can still work, but the life is damaged.

    In these three cases, if the component is completely destroyed, it can be detected and excluded in production and quality testing, and the impact is less. If the component is slightly damaged, it is not easy to be found in the normal test, in this case, it is often found to be damaged after several processing, or even when it is in use, not only the inspection is not easy, but the loss is also difficult to predict. The damage caused by static electricity to electronic components is no less than the damage caused by serious fire and explosion accidents.