Guru
Joined: 14/05/2006
Location: New ZealandPosts: 499
| Posted: 07:44pm 27 Nov 2009 |
Parallel caps are used to bypass (or couple) a wider band of frequencies.
Putting a 1uF electro in parallel with 100uF electro will probably not get you much, if any, improvement.
A 1uF mylar or polycarbonate in parallel with a 100uF electro will.
The main parameter you are looking for is the ESL or effective series inductance of the components.
Also, there are "issues" with just slapping caps in parallel without regard to their ESR or effective series resistance. You may find that they do not bypass at some "unexpected" frequencies (they go parallel resonant with each others inductance).
If you want to be sure your bypassing is doing the right thing, get the component parasitics and throw them into a circuit simulator. RFSim99 is free and easy to run.