A decoupling capacitor is used to decouple or separate one part of an electrical circuit or network from another. The capacitor shunts the noise of the other circuit elements through the capacitor, thus reducing its effects on the rest of the network. A decoupling capacitor is also known as a bypass capacitor because it bypasses the power supply and other impedance components of the network or circuit.
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The decoupling capacitor acts as a backup of the power current, giving up charge whenever the voltage dips. Electronics experts recommend the use of decoupling capacitors for each of the integrated circuits in a printed circuit board assembly. Some people claim that the use of decoupling capacitors is redundant, but they add to the safety and efficiency of the circuit.
Decoupling capacitors are also important in power connectors. A power line that connects to another circuit board will be considered a long power line. Long stretches of power wire benefit from decoupling capacitors, which must be placed at both ends of the wire. Decoupling capacitors are needed here because the long power line collects too much noise from the surrounding magnetic field, similar to an antenna gathering signals. The use of decoupling capacitors in digital circuits prevents electromagnetic interference radiation due to changes in the power supply current.
Decoupling capacitors shield a powered circuit from interruptions in the power supply. In many instances, the power supply may emit an AC signal that is superimposed on the DC power line. This is detrimental to the powered circuit. Using decoupling capacitors will prevent the powered circuit from getting this unwanted signal.
Decoupling capacitors also prevent a particular portion of a circuit from the effects of switching that may be occurring in another part of the circuit. The switching in a sub circuit may result in fluctuations in the power supply.
Decoupling capacitors have plenty of uses and benefits in PCBA and other products with electrical circuits.