Common ground processing of digital circuits and analog circuits There are now many PCBs that are no longer a single function circuit (digital or analog circuit), but are composed of a mixture of digital circuits and analog circuits. Therefore, it is necessary to consider the mutual interference between them when wiring, especially the noise interference on the ground wire. The frequency of the digital circuit is high, and the sensitivity of the analog circuit is strong. For the signal line, the high-frequency signal line should be kept away from the sensitive analog circuit devices as much as possible. For the ground wire, the whole PCB has only one node to the outside world, so The problem of digital and analog common ground must be dealt with inside the PCB, while the digital ground and the analog ground are actually separated inside the board, and they are not connected to each other, but at the interface (such as a plug, etc.) where the PCB is connected to the outside world.