What is the Electrical Return Path in a PCB?

One of the fundamental aspects of any circuit diagram is the return current path or electrical return path. In a circuit diagram and a schematic diagram, the path the current follows to return to the low potential side of a power source should be obvious, but it may not be so obvious in a PCB.

Signal Current Path and Return Current Path of 4-layer PCB. Return

Layout guidelines for good Return Path in PCB – RAM SYSTEMS

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Alternative Paths of the Return Current - In Compliance Magazine

The Path of Least Impedance: How to Use Return Paths for Better PCB Design - Technical Articles

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pcb design - PCB Review / Signal Return Path - Electrical Engineering Stack Exchange

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The Path of Least Impedance: How to Use Return Paths for Better PCB Design - Technical Articles

Return Current Path - Can Power Planes be used as Return Path?