Bypassing and Decoupling

Summary

The bypassing and decoupling is to prevent useful energy from being transmitted from one circuit to another circuit, and to change the transmission path of the noise energy, so that the quality of the power distribution network is improved. The most important point for using the decoupling capacitor is the lead inductance. Due to its low lead inductance, the surface‐mounted capacitor has a good performance than the through‐hole capacitor at high frequency. The response of the decoupling capacitor is based on the transient current. The explanation to the impedance response in the frequency domain is very useful in the aspect that the capacitor provides a supply current. In the actual circuit design, decoupling must be deployed for the clock and other periodic operating components. The self‐resonant frequency of the decoupling capacitor must be higher than the harmonic frequency of the clock to be suppressed.