What type of resisor/capacitor is not suitable for active filter design?

Discussion in 'The Projects Forum' started by McMurry, Jul 17, 2008.

  1. McMurry

    Thread Starter New Member

    Jul 5, 2008
    9
    0
    I am creating a low pass filter.
    I hope someone can help by telling me what type of cap/resistor (in terms of material, maybe?) that is not suitable in creating an active filter?

    thanks in advance.
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A metal film resistor has lower noise than a carbon film resistor. Use 5% or 1% tolerance.

    A metalized plastic film capacitor has extremely low distortion and has a 5% tolerance for accurate frequencies. They are good in active filters.
    Electrolytic, tantalum or ceramic capacitors have high distortion and have a very wide tolerance.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    As AG said, precision is key, as well as parts that don't drift over the long term.
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Depending on frequency, a wire-wound resistor might be a bad choice due to inductive reactance.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, if you account for the R, the L, and the parasitic C of the wirewound, then you can use it.

    If you discount the L or C of a wirewound in a filter, you will have a very unhappy time with it.

    The higher you go in frequency, the more parasitics come into play. An 0603 multilayer ceramic cap that measures 47pF at 1MHz can measure 150pF or more at 500MHz.
     
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