staying_well_grounded

　　Grounding is undoubtedly one of the most diffi cult subjects in system design. While the basic concepts are relatively simple， implementation is very involved. Unfortunately， there is no “cookbook” approach that will guarantee good results， and there are a few things that， if not done well， will probably cause headaches. For linear systems， the ground is the reference against which we base our signal. Unfortunately， it has also become the return path for the power-supply current in unipolar supply systems. Improper application of grounding strategies can cripple performance in high-accuracy linear systems. Grounding is an issue for all analog designs， and it is a fact that proper implementation is no less essential in PCB-based circuits. Fortunately， certain principles of quality grounding， especially the use of ground planes， are intrinsic to the PCB environment. Since this factor is one of the more signifi cant advantages to PCBbased analog designs， appreciable discussion here is focused on it. Some other aspects of grounding that must be managed include the control of spurious ground and signal return voltages that can degrade performance. These voltages can be due to external signal coupling， common currents， or， simply， excessive IR drops in ground conductors. Proper conductor routing and sizing， as well as differential signal handling and ground isolation techniques， enable control of such parasitic voltages.