decoupling / resevoir capacitors

[deoncarr]

Hi All,

I was looking at a simple schematic of a 9v DC supply divided into a +4.5v, -4.5v, virtual ground configuration and noticed quite large values for the decoupling capacitors (one placed between 9v and 4.5v and another between 4.5v and ground). Both were electrolytics 220uF each. The power supply was used to supply a single audio opamp ic.

Anyone no why such a large value for the caps? Seems a bit like overill (20 times over) to me. If anyone knows any different i would appreciate if you could set me straight.

thanks
Deon

 

[Klaus]

Maybe if you replace the word 'decoupling' with the word 'filter' it makes more sense?

Decoupling is used at individual IC's to decouple noise generated from within the IC to travel along the common power rails.

Filtering is used to reduce noise/ ripple from a power supply.

Klaus

 

[Phasor]

220u doesn't seem like such a large value to me :?