HV ceramic capacitors China : In theory (assuming capacitor is pure), the larger the capacitance, the smaller the impedance and the higher the frequency through. But in fact, capacitors above 1μF most are electrolytic capacitors, has great component of inductance, so if high frequency, the impedance will increase on the contrary. Sometimes we see a larger capacitance electrolytic capacitor in parallel with a small capacitor, the large one to pass low-frequency while the small one to pass high frequency. The effect of capacitor is to pass high-frequency and resistant low-frequency. The larger the capacitor, the easier low-frequency can through. It always used in filter,HV door knob capacitors (1000μF) filter low-frequency, and low capacitance (20pF) filter high-frequency. Users had the image of the filter capacitor as a "reservoir." As the voltage across the capacitor will not sudden change, therefore, the higher the frequency, the greater the attenuation. The capacitor just like a reservoir and the capacitance is like the water, reservoir will not change by adding a few water or evaporation. It translates the voltage change into current change, the higher the frequency, the greater the peak current, which buffer the voltage. Filter is just the process of charging and discharging. 

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