There are many types of capacitors, but no matter how they are classified, the basic principle is to use capacitors to show low resistance to alternating signals. The higher the frequency f of the alternating current, the lower the impedance of the capacitor. The main function of the bypass capacitor is to provide a low-impedance path for the AC signal; the main function of the decoupling capacitor is to provide a local DC power supply to the active device to reduce the propagation of switching noise on the board and guide the noise to the ground. After adding decoupling capacitors, the voltage ripple interference will be significantly reduced; filter capacitors are often used in filter circuits. (read more about filter capacitors)