What are different types of grounds in electronic circuits?

Answer 1

A "ground" in electric or electronic circuits, is a theoretical entity that is at zero volts everywhere. The Earth itself is often used as an approximation to this, and sometimes grounds are called "Earth" connections. There is only one ideal ground.

However, in electric and electronic engineering, much of the challenge is dealing with real-world things that differ from the ideal or theoretical model. Grounding is one of those where the difference between the ideal and real-world must be addressed. The topic of grounding and shielding is complex.

Engineers take complete courses in grounding and shielding and very senior engineers can puzzle over grounding issues for days or weeks, so it is not possible to give a comprehensive answer in a short space.

It is useful to think of some of the different functions of a ground:

1. A ground provides a return path for current

2. A ground provides a reference point for measuring other potentials or signals

3. A ground provides a safety connection for metal enclosures

4. A ground provides a shield to screen out electromagnetic noise, as in a coaxial cable or Faraday cage

5. A ground plane is needed for an antenna to function properly

6. In electronic circuits, the ground is often used as a heat sink to dissipate heat from components

It is often a good idea to use different "grounds" for different functions. For example in electrical wiring both the neutral and protective ground wires are ground connections, but one serves as a current return path and the other is a safety connection. There are very good practical reasons to have these implemented as two different wires.

In electronic circuits, different grounds are often used because real ground paths have resistance, inductance and capacitance and signals take time to travel from one part of the circuit to another--especially when thin copper traces are used on a circuit board.

The primary concern in real-world grounding is considering current flow and current paths. For example in a PC board, power returns and high-speed clock signals usually use different copper ground traces than low-level audio or sensor signal reference grounds, so that the transient current from switching does not affect the ground reference for tiny signals. The grounds are tied together at one point, so that there is no circuit path for current to travel between the paths, but they are at the same potential voltage.

None of this would be necessary if we had an ideal ground--zero volts everywhere, with no impedance between any two points.