What Capacitors Should I Use

Discussion in 'General Electronics Chat' started by bumba000, Oct 5, 2016.

  1. bumba000

    Thread Starter Member

    Oct 7, 2015
    72
    2
    Hi All,
    I have been working on this 9-band filter found elsewhere on the interweb. I have the buffer and the first three filters built. It works pretty well, but I'm using electrolytic caps. Looking at the schematic the capacitors used appear to be tantalum. The part used in schematic is: C-EUC0805K
    Is this correct? Are all caps supposed to be tantalum?

    I understand that it sounds like I already know the answer is yes - tantalum. The problem is that I can not find any through hole 10nF tantalum caps. I can find them in surface mount. Is there such a thing as through hole 10nF Tantalum capacitors?

    Thank You,
    John
     
    Last edited: Oct 5, 2016
  2. dl324

    Distinguished Member

    Mar 30, 2015
    3,250
    626
    Didn't look at your attachment, but the caps band pass/notch filters would typically be low leakage precision types.
     
  3. bumba000

    Thread Starter Member

    Oct 7, 2015
    72
    2
    I understand your response, but then again I really don't. I am looking at SMD tantalum caps now. Is this what I need?

    Thank You, John
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
    3,250
    626
    It depends. How narrow are the bands? Tantalum caps usually have a wide tolerance; on the order of -20/+80%.
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    Don't upload .sch files. Post graphics files such a .jpg, .png etc.

    Don't use tantalum for such applications. Mylar or other poly- type capacitor is fine.
     
  6. bumba000

    Thread Starter Member

    Oct 7, 2015
    72
    2
    I included the sch so that you can see what I'm seeing when clicking on a component. That doesn't work with jpg, png etc...

    I have used ceramic capacitors but the circuit doesn't seem to work properly with them. Could this be due to the virtual ground? 50hZ, 120hZ, 250hZ etc... pretty tight I guess.
     
  7. bumba000

    Thread Starter Member

    Oct 7, 2015
    72
    2
    Ok, so I haven't been able to find a capacitor in a schematic that uses a symbol like the caps in this schematic. I've researched the "device" shown in properties when clicking on cap symbol. It says that it's a tantalum capacitor. The schematic seems to suggest polar direction. When I tried ceramic caps, it didn't work. Using electrolytic works but I don't have any 10nF sizes. I ordered today 120 tantalum SMD caps. 10nF, 100nF and 1uF. It was a great deal anyways, but I see you're saying not to use them. I have mylar on hand but of course not the required sizes. Also they don't care about polarity. will that be a problem in the particular circuit?

    Thank You, John

    [​IMG]
     
  8. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    Then something isn't right. Maybe you used the incorrect capacitance values.

    Yes.

    You need to use non-electrolytics in any kind of audio frequency filters.

    There are places where we use electrolytics such as in power supply filters and in DC blocking capacitors between stages. We use electrolytics because non-electrolytics would be enormous in physical size. In all such cases, you have to ensure that the polarity of the bias across the capacitor matches the marking on the capacitor. In other words, the more positive potential in the circuit goes to the positive lead of the capacitor.
     
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