I've seen cases when for example a 0.1uF capacitor has been placed in parallel with a 10uF capacitor. Would this be equivalent of having a 10.1uF capacitor all alone since capacitance add up in parallel? Does the addition of capacitance in parallel somehow not apply in this senario?

 

Hello,

The 10uF will suppress switching surges, the 0.1 uF will suppress RF surges.
Read the following thread for more info on decoupling:
https://forum.allaboutcircuits.com/threads/decoupling-or-bypass-capacitors-why.45583/

Bertus

 

Yes, 10μF in parallel with 0.1μF gives 10.1μF.
But the tolerance of the 10μF is about ±10% or ±20% to begin with, certainly not ±1%. So what gives?

Obviously, there is much more than meets the eye otherwise why do electronics engineers in the know-how do it?

Read this to learn more:

https://www.intersil.com/content/dam/Intersil/documents/an13/an1325.pdf

 

A good part of the reason for placing a small ceramic capacitor in parallel with a larger electrolytic capacitor is that the two types have very different behavior over frequency.

The electrolytic capacitor does a good job of decoupling at frequencies below a megahertz or so, but becomes a series resonant circuit (due to its internal effective series inductance) at some frequency above that, and thereafter acts as an inductor instead of a capacitor, at frequencies above that point.

The ceramic capacitor, due to its construction and physically small size, has its self-resonant point at a much higher frequency than the electrolytic and therefore can perform better in decoupling at high frequency. Putting the two types of capacitor in parallel thus allows the decoupling to cover a broader spectrum.

The fact that 10 μF + 0.1 μF = 10.1 μF is of no importance.

 

 

Really interesting with the different resconance frequencies of the capacitors. Thanks for the help!