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power supply filtering questions

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Thread Starter

msoof

Joined May 28, 2008
6
hi all,

Assuming i am filtering noise on a powersupply to a linear regulator IC,
is it ALWAYS necessary to have a bypass capacitor BEFORE the decoupling LC network?

thanks alot
:)
 
Wendy

Wendy

Joined Mar 24, 2008
23,797
I'm not too sure about the decoupling LC network being necessary, but a cap is always a good idea. Where are you getting the info about the decoupling network from?
 
SgtWookie

SgtWookie

Joined Jul 17, 2007
22,230
If you're talking about a cap to ground, then a series inductor, then a cap to ground - yes.

That is a classic "Pi" filter. Without the 1st cap, the output stage of the linear regulator may become damaged due to polarity reversals across the inductor.

The inductor keeps the current flowing at a fairly steady rate. The capacitors keep the voltage levels relatively constant.
 
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