Choose large or small capacitors, in the case of low frequency noise and high frequency noise?

Regarding this issue, we have to understand the impedance frequency characteristic curve of the capacitor!

*F**igure 1** **Capacitance impedance frequency characteristic curve*

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It can be seen from the *F** igure 1* above. It is correct if we only consider the Capacitance component.

Because the larger the capacitance component, the lower the resonance point frequency, the more suitable it is to filter out low frequency noise. The smaller the capacitance component, the higher the resonance point frequency, and the more suitable it is to filter out high frequency noise.

What is the impedance characteristic of a capacitor with a different capacitance under the same package if only the capacitance component is considered?

*Figure 2 The larger the capacitance component, the lower the resonance point frequency*

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However, if you consider the ESL component, the above figure needs to be corrected, as shown below.

*Figure 3 Capacitance impedance frequency characteristic curve under the same package*

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Obviously, the impedance frequency characteristic curve of the 0603 0.01uF capacitor is completely covered by the characteristic impedance curve of the 0603 1uF capacitor.

In addition to reducing the impedance of the filter circuit, the 0603 0.01uF capacitor actually does not play any role!

What is the impedance frequency characteristic of a capacitor of the same capacity in different packages?

*Figure 4 Impedance frequency characteristic curve of capacitors with the same capacity and different package*

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Obviously, the impedance frequency characteristic curve of the 0603 0.01uF capacitor is completely covered by the characteristic impedance curve of the 0402 0.01uF capacitor.

In addition to reducing the impedance of the filter circuit, the 0603 package capacitor does not actually play any role!

**Based on the above conclusions, we can see that:**

In order to filter out low frequency noise, in the case of the same package, the capacity needs to be considered, and a large capacitor is selected;

In order to filter out high-frequency noise, it is necessary to consider the package in the case of the same capacity, and select a small package capacitor0

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