Where is the ground located in a PCB?

I am learning to design a multiple layer board for a medical device, and have a question about where the ground should place.
  • On a simple PCB, it’s often done as a ground fill. The fat, thick areas are often ground.
  • On a 2-layer PCB, you may have power fills as well. You can use generalizations like this to find the ground more easily if you’re examining a PCB, but you can’t know for certain without analyzing the circuit. It’s also typical for ground to be connected at the negative end of large electrolytic capacitors. Again, not in every case, but it’s a place to look for it.
  • Complex, high-speed, and high-density PCBs are multi-layer. Typically, at least one layer will be devoted to a ground plane. This is critical for both RF and high speed digital circuits such as PCI Express, USB, SATA, DDR DRAM, Ethernet, etc. Because critical signals are routed on impedance-controlled lines referenced to a ground plane. For us, we usually run microstrip lines on the top or bottom of the PCB, so there’s a ground layer right below the top and/or bottom layer.

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Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.
Picture of Oliver Smith

Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.

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