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Electronics => Beginners => Topic started by: Fantasma25 on February 26, 2014, 01:37:36 am

Title: Parallel capacitors?
Post by: Fantasma25 on February 26, 2014, 01:37:36 am
Why so many circuit designs have two or three or more small capacitors in parallel between VCC and GND instead of having just medium one? I'm talking about something like this. Thank you!

(http://imageshack.com/a/img20/7587/om55.png)
Title: Re: Parallel capacitors?
Post by: c4757p on February 26, 2014, 01:42:32 am
Decoupling capacitors. The traces delivering power to the chip will have some inductance, so if it takes a sudden gulp of current, the voltage at the power pin will drop. A capacitor is put very close to each power pin to provide a local store of power to counteract this.

Another reason to parallel capacitors is that smaller capacitors typically perform better at high frequency. If you need 100uF, but you need it to work up to high frequency, you'll have to put some small ceramic capacitors next to the big electrolytic capacitor.
Title: Re: Parallel capacitors?
Post by: Fantasma25 on February 26, 2014, 01:50:05 am
Decoupling capacitors. The traces delivering power to the chip will have some inductance, so if it takes a sudden gulp of current, the voltage at the power pin will drop. A capacitor is put very close to each power pin to provide a local store of power to counteract this.

Another reason to parallel capacitors is that smaller capacitors typically perform better at high frequency. If you need 100uF, but you need it to work up to high frequency, you'll have to put some small ceramic capacitors next to the big electrolytic capacitor.

Thank you! Now I get it  8)