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When using decoupling capacitors to deal with multiple frequencies, is it better to use multiple capacitors for the respective frequencies, or should a single capacitor be used with the value selected to deal with the frequencies collectively?Also, are there any problems with adding multiple capacitors?
It is recommended that multiple capacitors be used for different frequencies. As for problems, if multiple capacitors having self-resonant frequencies that are far apart are used, antiresonances may occur between those frequencies, and there are concerns that noise characteristics may be worsened at the antiresonance frequencies. Also, when arranging multiple capacitors, it is preferable that capacitors with higher self-resonant frequencies (mainly small-value capacitors) be placed closer to the IC; if instead capacitors with higher self-resonant frequencies are positioned further away, the line inductance to the capacitors will cause the self-resonant frequency to shift to lower frequencies, and the intended characteristics may not be obtained.