[sdiy] How to Determine Value of Power Supply Decoupling Caps?

[Oren Leavitt]

Hi Scott,

For every PC board, I generally use a 22uF electrolytic paralleled with 
a 0.1uF ceramic cap on each rail where the power supply connects to the 
PCB and use additional 0.1uF ceramic caps close to the the power pins of 
each op-amp, CMOS or other IC - at least one cap every few ICs.
I may add an extra electrolytic by noisy buggers like 555s etc.
A lot of us use those small 'multilayer' ceramics which come in axial or 
radial form.
These values work great for most general purpose stuff like synth circuits.

Look in IC data sheets - sometimes there are bypassing recommendations 
for certain ICs.

HTH,
Oren

Scott Stites wrote:

>Hi List,
>
>This is something I've been wondering about for a while.  I know that one
>should use caps with twice the voltage rating that one would expect the caps
>to bear, but what criteria do you use to determine the capacitance value of
>the caps for filtering on power entry of a module?
>
>Do you base it on the amount of current the module draws, what the module is
>doing, an educated guess, all of the above or none of the above?
>
>Any guidance most welcome,
>
>Thanks,
>Scott
>
>
>  
>

-- 
Oren Leavitt
oleavitt at ix.netcom.com