The Q value of these two kinds of capacitors is very low, and the frequency selectivity is not strong, which is very suitable for board-level filtering.
The selection of high-frequency small capacitors is somewhat troublesome, and needs to be calculated by frequency bands. The frequency range that needs to be decoupled can be divided into several sections, one section is calculated separately, and multiple capacitors with the same capacitance value are used in parallel to meet the impedance requirements, and different capacitance values ​​are selected for different frequency bands. However, in this method, the division of frequency bands should be continuously adjusted according to the calculation results. Generally, it is enough to divide into 3 to 4 frequency bands, which requires 3 to 4 capacitance levels.