PCB design for op amp

Discussion in 'General Electronics Chat' started by drkblog, Oct 20, 2012.

  1. drkblog

    Thread Starter Member

    Oct 4, 2012
    109
    0
    I'm trying to design a PCB for a couple of op amp working both as amplifiers and filters. Working with signals from DC to 3kHz. Questions are:

    1. Is there a recommendation for the vias (like size, maximum length)?
    2. Should I place the common GND copper area around the board?
    I have been trying with Ultiboard and came up with something like this:


    [​IMG]
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,772
    931
    http://www.armisteadtechnologies.com/trace.shtml
    ...to calculate current flow limits and design for ample width on power carrying traces.

    If you have noise pick up problems then full board ground planes and additional shielding can be applied to minimize it. Otherwise, a simple sealed metal enclosure is sufficient for shielding purposes and environmental protection.
     
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  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    The board design depends on the voltage level of the signal, but for 3khz bandwidth it doesn´t matter how long the traces are etc.
     
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  4. nigelwright7557

    Senior Member

    May 10, 2008
    487
    71
    I use vias with 1mm holes.

    Be very careful with audio to keep the power supply and audio ground in a star configuration. Failure to do so will see power supply hum on the audio.
     
  5. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    In general, keep the trace lengths to the op amp summing (-) junction as short as possible and keep high level input or output signals far away. Short traces are more important the neatness. The summing junction is very sensitive to stray signal/noise pickup and parasitic capacitance.
     
  6. drkblog

    Thread Starter Member

    Oct 4, 2012
    109
    0
    What is a star configuration?

    About the length of traces: I grouped the components of each op amp near the pins of the IC and then let the program autoroute. I have three ICs (using 5 op amp) a couple of 5x2 connectors within a PCB of 112mm x 90mm (4 2/5 x 3 1/2 inches).
     
  7. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    That's ok if you group the components that go to the summing junction as close to that summing pin as possible.
     
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