I have used the 78series regulators on multiple occasions but do not know why they use the cap values that is mostly the case.(10n,100n,etc)

Why are these specific values used? Is there a way to calculate the exact values for a specific situation?

 

Konstable,

These are to prevent the 3-terminal regulators from oscillating. The values are not critical, but should wired physically as close to the regulator pins a practical. Look at the manufactures' datasheets for recommended values.

Ken

 

Thanks Ken,

So the values aren't related to specific filtering frequencies? And why then are there almost always a 10n and 100n together?

 

Actually, they're usually 0.1uF and 1uF. The 0.1uF is generally a ceramic or tantalum capacitor, where the larger cap is electrolytic. The smaller cap takes care of the high frequency noise component, and the large cap is to smooth out lower-frequency transients.

 

For general applications the values are not critical. If you have high switching current
you should look at the application notes and the capacitor specifications.

I usually use a 0.1uF X7R ceramic capacitor in parallel with a 1-10uF capacitor. For
capitors <=4.7uF I use an X7R ceramic capacitor otherwise I would use a tantalum capacitor.

(* jcl *)

 

All i know in practice i use a lot capacitor.

 

You also want to consult the datasheet for recommended values and types of caps. Some Vregs do not like ceramic caps on the output.