Capacitor in parellel

Thread Starter


Joined Jan 25, 2007
Dear forum member,

I saw the statement below from the website below, can some one give a sensible reason for me why??

"The frequency of the ripple can have a role in choosing the capacitor value. Rule of thumb is the higher the frequency, the smaller the bypass capacitor you need. If you have very high frequency components in your circuit, you might consider a pair of capacitors in parallel"



Joined Jan 28, 2005
The phenomenon that has to be dealt with when it comes to capacitors is ESR (Effective Series Resistance). The larger valued capacitors tend to exhibit larger values of ESR. This ESR causes the capacitor to become predominantly resistive above a certain frequency depending on the capacitance value. Lower valued capacitors have correspondingly lower values of ESR and therefore they do not become resistive until the ripple frequency is much higher.

By placing two similar valued capacitors in parallel, the effective ESR of the two capacitors is roughly cut in half. This is due to the fact that equal valued resistors when placed in parallel are equivalent to the resistance/2. At the same time the resistance is halved, the capacitance is doubled. That is because capacitance in parallel is additive.