A decoupling capacitor is a capacitor used to decouple one part of an electrical network (circuit) from another. Noise caused by other circuit elements is shunted through the capacitor, reducing the effect it has on the rest of the circuit.

What is the purpose of decoupling capacitor?

Decoupling capacitors help to provide a local instantaneous charge source that prevents the voltage source from dipping and a bypass path that dampens ringing. Noise on the PDS is also locally damped, helping the local circuit remain unaffected by ripple on the power plane that could otherwise disturb the circuit.

What capacitors to use for decoupling?

Larger electrolytic capacitors (1 to 100 μF) are used to decouple low-frequency noise. These capacitors act as charge reservoirs to fulfill the instantaneous charge requirements of the circuit. Such capacitors should not be placed more than 2 inches away from the IC.