Bypass Capacitors quick question?

Discussion in 'General Electronics Chat' started by Tony Elliott, May 25, 2016.

  1. Tony Elliott

    Thread Starter Member

    May 8, 2015
    140
    2
    image.jpeg image.jpeg
    Hi,
    I am using a mains supply +/- 12 so I don't need the bypass capacitors right?
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,387
    1,605
    Wrong.

    The caps shown should be thought of as a minimum, a starting point. That is what worked for the designer on his board, your board may need more.

    Seems these were drawn without and hints as to where to place them. I would start with the 10 uf where the power enters the board. I would put a pair of the 0.1 caps with them, and another pair on each op amp. You need more than the schematic implies but here more is usually better and rarely if ever hurts.
     
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  3. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    Never skimp on bypass capacitors.
     
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  4. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,790
    Bypass capacitor arrangements work best when you have several values in parallel. The higher values ( >1 μF) typically supply transient current demands of the adjacent chips, while smaller values (<= .1 μF) supply a path to ground for high frequency transients. Putting the three values in parallel is different than just having one capacitor of the equivalent value. eg 1 μF || 0.1 μF || 0.01 μF behaves differently than a single 1.11 μF capacitor assuming such a thing was available.

    You can work out the reactance of a capacitor at various frequencies via

    X_C=\frac{1}{2\pi f C}
     
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  5. Tony Elliott

    Thread Starter Member

    May 8, 2015
    140
    2
    Thank you I'll use the caps & look at values:)
     
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