In the PCB proofing, the reasonable and effective use of components is an important guarantee for the performance and quality stability of the circuit board. So, what problems should be paid

attention to in the use of components in the PCB proofing process?

1. limit the output current to avoid the locking effect of the CMOS circuit: the locking effect means that there is a parasitic PNP transistor and NPN transistor on the internal structure of the CMOS

circuit, and between them, a parasitic PNPN thyristor structure is formed. A common solution is to use a resistor to separate each output from its cable, and to use two high-speed switching diodes to

clamp the cable to the VDD (drain power) and VSS (source power).

2. the use of filter network: sometimes a long input cable is required between the CMOS circuit system and the mechanical contact, which increases the possibility of electromagnetic interference,

and the use of filter network should be considered.

3. the composition of the RC network: for the sensitive input of bipolar devices, the use of a resistor with a large resistance value and a RC network of at least 100pF capacitors can reduce the impact

of electrostatic discharge.

4. avoid CMOS device input pin suspended: this is because once the input pin suspended, the input potential will be in an unstable state, not only will destroy the normal logic of the circuit, but also

easy to produce electrostatic breakdown, external noise interference and other phenomena. The redundant input ends should be dealt with separately according to the function of the circuit.