ESR and Bypass Capacitor Self Resonant Behavior
Improvements in bypass capacitor fabrication and assembly techniques have resulted in higher self-resonant frequencies. The results have sparked many debates on how to best take advantage of these higher frequencies and lower ESRs, while other issues (such as anti-resonant peaks) have been largely ignored. This paper explores the effects of lower ESRs, the true value of impedance minimums, and how to obtain better results using more capacitors. Several examples based on various cases are given, each supported by calculations, results, and illustrations. Information on achieving flat frequency responses is provided in detail, with a link where you can download UltraCAD’s Bypass Cap Impedance Calculator that was used in the analysis. Detailed analysis, graphs, and results are provided in the appendices.
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