What principles should be followed when selecting electronic components? Remember these eight points, don't step into the pit

For engineers, the correct use of components is a particularly important part of their work and holds an important position. Electronic components are the most fundamental component of electronic equipment. The malfunction of electronic devices is largely caused by the characteristics, quality, or improper use of components. Therefore, the correct use of electronic components is a prerequisite for ensuring the reliability of electronic equipment. Reliability design is the process of using components that can still ensure high reliability in the worst-case scenario.

1: The preferred order for integrated circuits is VLSI → Large scale integrated circuits → Medium scale integrated circuits → Small scale integrated circuits.

2: Try to choose plastic shell integrated circuits as much as possible, which is beneficial for heat removal.

3: The selected integrated voltage regulator should have overheating and overcurrent protection circuits inside.

4: The selection of Very Large Scale Integration should pay attention to the test and selection of the circuit, otherwise it will affect the reliability of use.

5: When using integrated circuit MOS devices, the following points should be noted:

1) The current load capacity of MOS devices is relatively low, and the capacitive load will have a significant impact on the operating rate of the device. 2) For time sequence and Combinational logic, the maximum frequency of the equipment used shall be~3 times higher than the application position of the circuit.

3) For input interfaces, the device has good anti-interference performance. 4) For the output interface, the device has good driving ability.

6: When using CMOS integrated circuits, the following issues should be noted:

1) The amplitude of the input voltage of CMOS integrated circuits should be controlled between the power supply current and the leakage power supply current. 2) The CMOS integrated circuit power supply current VSS is at low potential, while the leakage power supply current VDD is at high potential and cannot be inverted. 3) When the input signal source and CMOS integrated circuit do not require the same set of power supplies, first connect the CMOS integrated circuit power supply, and then connect the signal source; Firstly, cut off the signal source, and then cut off the power supply of the CMOS integrated circuit.

4) When connecting long or large integration or filtering capacitors at the input (output) end of CMOS integrated circuits, a current limiting resistor (1-10k Ω) should be connected in series at its input (output) end to limit its input (output) current to within 10ma. 5) When the clock signal input to a CMOS integrated circuit is overloaded and causes slow edges, it not only leads to data errors, but also increases power consumption and reduces stability. Therefore, it can be input to add a Schmitt trigger to change the edge of the clock signal.

7: All different input terminals in CMOS integrated circuits cannot be idle, and according to their working functions, the following issues should generally be addressed:

1) The excess terminals of the gate and non gate should receive VDD or high-level resistance through 0.5-1M Ω.

2) The excess terminals of the OR gate and the NOR gate should be connected to the VSS or low frequency through a 0.5-1M Ω resistor. 3) If the working speed of the power supply is not high, do not particularly consider power consumption. Multiple terminals can be connected in parallel with application terminals with the same function on the same chip. It should be emphasized that there have been some changes in transmission characteristics compared to individual applications.

8: When using integrated operational amplifiers and integrated comparators, the following issues should be noted:

1) When the integrated operational amplifier without internal compensation applies negative feedback, compensation measures should be taken to avoid Self-oscillation. 2) When the integrated comparator is used in open-loop applications, Self-oscillation sometimes occurs. The main measure is to implement power decoupling and reduce wiring capacitance and inductance coupling. 3) When the power is high, it is necessary to increase the buffer stage. When the output end is directly connected to the outside of the circuit board, attention should be paid to overcurrent protection at the output end. 4) The input terminal requires overvoltage protection, especially when the input terminal is directly connected to the outside of the circuit board, overvoltage protection measures must be taken at the input terminal.

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