1 Introduction

The term “ground” in the context of electrical engineering took shape with the invention of modern utility electricity and telegraph systems, where it was discovered that the Earth ground could be used to carry the return current.

In modern-day utility electricity standards, an uninterrupted Earth ground wire is required that runs from the source to the loads. This ground is also referred to as equipment ground. The purpose of the equipment ground is to prevent metal parts from being energized in situations such as broken insulation of the main conductors. Sometimes people also refer to the grounded neutral as “ground”. Strictly speaking, a distinction should be made between the two. Neutral completes the loop with “hot” or “line” and is the return path for the load current. Although it is connected to Earth ground at the main distribution panel, it is prohibited to do so at the point of load such as an outlet.

Figure 1-1 is a one-line wiring diagram for a typical household electrical system in the US. It shows the connection from the breaker panel to various loads, as well as how grounding should be connected for the loads. A load may be any common household appliance, as well as electrical outlet.

In the semiconductor industry, the term “ground” is used even more loosely. Ground often simply refers to a common connection without any physical connection to Earth ground whatsoever. In other words, it has nothing to do with Earth ground. After all, electrical standards generally do not require Earth ground for low-voltage DC systems, a domain which a majority of semiconductor circuits fall into.