Engineers use the word “ground” in every electronic circuit to denote some part of a system or structure that is “neutral,” or zero potential. Unfortunately, we often think of circuits and systems, especially those with both analog and digital signals, as having more than one ground. This concept gave rise to a recent discussion on a signal-integrity online community

Engineers and PCB designers often mention various types of grounds and methods for connecting them together.

The kinds of grounds mentioned in this discussion include:

Logic ground
Analog ground
Chassis ground
Safety ground
Earth ground

Methods proposed for connecting these various “grounds” cover a broad range of options including:

Connecting them at only one point.
Cutting the ground plane under a mixed signal component
Connecting them with capacitors.
Segmenting the ground plane in a PCB such that there is only a narrow connection at one place between the analog and digital sides of the design.
Separating the analog and digital grounds.

These seemingly conflicting methods for dealing with ground can be a bit confusing. We’ll start by clarifying what ground is, which should reduce the confusion.