Thursday 5 April 2018

How to calculate ESR of capacitor

ESR is the short form of equivalent series resistor.
Theoretically Ideal capacitor would be lossless and have an ESR of zero. As being ideal capacitors and Inductor has a series resistor, this resistance is defined as the equivalent series resistance (ESR).

For calculating ESR of any capacitor we should know dissipation factor i.e. DF (Dissipation factor is known as the tangent of the loss angle and is commonly expressed in percent) and capacitive reactance Xc = (2* π*f*C)
ESR=DF*XcDF/(2* π*f*C)
For example if you want to calculate ESR of ceramic capacitor of value 0.1uF/50V
Dissipation factor DF is 5% at 120Hz

= 66.34Ohms
so the ESR of ceramic capacitor of 0.1uF/50V will be 6.6mOhms
For Power integrity and Signal integrity analysis,ESR is the important factor.


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