Rather, he would add to the original. However, single-supply operation can force some differences into the overall design. One key element in analog single-supply systems is your choice of a reference point. If your circuit has to deal with bipolar signals and single-supply components, you must create a new reference point. The origins of noise Simply understanding the mechanisms that generate ground noise is crucial to minimizing that noise.
Digital circuits create current spikes when signals change state and on clock edges.
Analog circuits create current spikes when load currents change and during slewing. Thus, voltage differences can exist between the local ground as compared to the reference ground. A dc offset is created between reference and local ground by a constant current impressed across the ground-return resistance. This offset voltage can also be dynamic, as is the case with digital logic that is frequently switching, which ultimately introduces a high-frequency ac component into the local ground system. The most obvious reference choice is halfway between V CC and ground, typically 2.5V for a 5V system supply.