power supply filtering questions

Discussion in 'General Electronics Chat' started by msoof, May 28, 2008.

  1. msoof

    Thread Starter New Member

    May 28, 2008
    6
    0
    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
    :)
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    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?
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    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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