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Printed Circuit Board Power Bus Decoupling Questions

2. What is the best method for connecting decoupling capacitors if my PCB does not have a power plane?

Generally, it is best to provide a low-inductance connection between the decoupling capacitor and the power pins of the active device being decoupled. Small loop areas and wide traces yield lower inductances.

To provide additional isolation from the rest of the power bus, it is sometimes desirable to use two decoupling capacitors mounted some distance apart. More information can be found in the LearnEMC Tutorial: Power Bus Decoupling Guidelines for Printed Circuit Boards without Power Planes.


[1] C. R. Paul, "Effectiveness of Multiple Decoupling Capacitors," IEEE Trans. on Electromagnetic Compatibility, vol. 34, no. 2, May 1992, pp. 130-133.

[2] T. Zeeff, T. Hubing, T. Van Doren and D. Pommerenke, "Analysis of Simple Two-Capacitor Low-Pass Filters," IEEE Transactions on Electromagnetic Compatibility, vol. 45, no. 4, Nov. 2003.