The selection of components is based on standardization, generalization and localization. Select qualified components that meet the requirements of the circuit parameters; use is to use scientific methods to apply the selected components to the circuit to achieve various technical indicators of the design circuit.
Electronic components are basic circuit units that perform predetermined functions without being detachable and decomposed, such as resistors, capacitors, discrete semiconductor devices, semiconductor integrated circuits, microwave components, relays, magnetic components, switches, electrical connectors, filters, sensors , Fiber optics, etc. Practice has proved that in electronic equipment, failures caused by improper selection of components account for 44% to 67% of the total failures, while failures caused by the quality of the components themselves account for only 33 to 46%, as shown in the following table. Therefore, component selection occupies an important position in circuit design, and designers must attach great importance to it, carefully calculate and design carefully.
The specifications, models and parameters of each component marked on the circuit are the basis for the selection of electronic components. For products that have been finalized, the components on the schematic diagram are designed, developed, and trial-produced and put into production. The parameters are determined according to the methods of qualitative analysis, quantitative estimation, and experimental adjustment. Under normal circumstances, replacement is not allowed. Or changed. However, for electronic product developers, amateurs, and maintenance personnel, due to the influence of many factors such as objective conditions, under the condition of meeting the technical requirements and specifications, if the amount is small, the components can be selected flexibly and flexibly. In some specific cases, even if there is a schematic diagram, some components are not fully labeled with parameters, such as electrolytic capacitors only marked with capacitance but not withstand voltage, so they must be reconsidered in the power circuit; product use site conditions and technology If the data does not match, some components can be adjusted to adapt to the actual environment; individual components cannot be purchased locally, and components that meet the requirements can be used as substitutes; during the repair process, if some components are found to be unreasonable, they need to be replaced with appropriate ones. Components.