TABLE OF CONTENTS A fundamental property of any electronic or electrical circuit is that the voltages present within it are referenced to a common point, conventionally called the ground. (This term is derived from electrical engineering practice, when the reference point is often taken to a copper spike literally driven into the ground.) This point may also be a connection point for the power to the circuit, and it is then called the 0V (nought-volt) rail, and ground and 0V are frequently (and confusingly) synonymous. Then, when we talk about a five-volt supply or a minus-twelve-volt supply or a two-and-a-half-volt reference, each of these is referred to the 0V rail.
At the same time, ground is not the same as 0V. A ground wire connects equipment to earth for safety reasons, and does not carry a current in normal operation. However, in this chapter the word grounding will be used in its usual sense, to include both safety earths and signal and power return paths.
Perhaps the greatest single cause of problems in electronic circuits is that 0V and ground are taken for granted. The fact is that in a working circuit there can only ever be one point which is truly at 0V; the concept of a 0V rail is in fact a contradiction in terms. This is because any practical conductor has a finite non-zero resistance and inductance, and Ohm s Law tells us that a current flowing through anything other than a zero impedance will develop a...
