Typical PCB protection devices mainly fall into the following categories:
(1) Resistor-capacitance components. By connecting resistance-capacitance elements on each signal line, it can play a certain role in PCB shielding. A series resistor can suppress the instantaneous peak current, and a parallel grounded capacitor can limit the instantaneous peak voltage.
(2) Clamping diodes. The transient voltage between the positive and negative polarities can be clamped within a certain range through two diodes, and the series resistance can provide the power load, thus playing the role of positive and negative PCB protection.
3) Zener diode. Although the Zener diode is not specially designed for PCB applications, its working characteristics determine that it has a certain positive and negative PCB protection effect. Its downside is. The N junction is small, so it cannot withstand a large peak current. In addition, the parasitic capacitance generated by it is large, which may affect the normal operation of the circuit.
(4) Transient voltage suppressor. Transient voltage suppressor, also known as TVS tube, is a solid-state diode specially designed for PCB protection. The biggest feature of TVS tube is short response time and small leakage current, which is an ideal protection device.
(5) Gas discharge tube (GDT). Gas discharge tubes use glass or ceramics with a certain airtightness as the outer shell. The tube is filled with a stable gas such as neon or argon to maintain a certain state of insulation. The advantages of gas discharge tubes are that the insulation resistance is large, the parasitic capacitance is small, and they can recover by themselves, but the disadvantages are that the response speed and life are not ideal, and the electrical properties will gradually decay with time.
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