Ground loops

摘要

I design audio circuits. My mentor taught me to avoid ground loops at all costs, yet in digital products I see a solid ground plane holding hundreds of circuits. Between boards, I see a web of ground-referenced connections shooting off in all directions. How can this possibly work? Imagine two parts of an electronic system. When device A sends to B, a signal current flows between them. At the same time, an equal and opposite current, called the returning signal current, flows back to A through the power or ground system. Current always makes a loop in that way. A ground loop is a situation where there exists more than one path for the flow of returning signal current.