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Bypass network

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  • Bypass network

    Bypassing supply at analog devices is to reduce existing noise in power supply. But how about the positioning of the caps if two ICs are close to each other? Weren`t 50% of the caps redundant?
    I place 2 ICs and their baypass caps close to each other. Would i get the same result if i only use 3 caps instead of 6?

    The 2 ICs are close to each other again, but the bypass networks are placed on the opposite. Do i need in that case both bypass networks because of the spatial seperation?

    Bypass Caps.pdf

  • #2
    The primary role of the decoupling capacitors is to be a close, low impedance current source, which keeps the voltage at the IC stable.

    If you have 2 ICs you will have twice the current draw. Optimally you will want to use twice the capacitors. If you know what you are doing you might be able to make a compromise and save some of the capacitors, but just removing half of them is not optimal and might cause problems if the circuit is decoupling sensitive.


    • #3
      Ok that makes sense. I thought about using bypass caps at analog components as filter for the power supply. And thus "clean" it and supply nearby ICs.
      But since my analog signals have also a square shape, the current drawn by the devices plays a crucial role especially at the fast edges.

      I will give it a try and see how good theory matches up with the real assembly.


      • #4
        The power supply output needs to be filtered as close to the output itself as possible - doing it differently is normally wrong. At the supplied components end you should already have a nice clean rail.