Types of Capacitors and their selection

Discussion in 'General Electronics Chat' started by SPQR, Nov 15, 2012.

  1. SPQR

    Thread Starter Member

    Nov 4, 2011
    Hello all,
    I've been working on a new project to help me (and other newbies) on the types and selection of capacitors. I've never been sure why a person might choose capacitor X over capacitor Y in a given circuit.

    When I'm trying to learn a new field, I often find that having a "30,000 foot view" of the field can be helpful. So I went to Wiki, and read a bit on capacitors, then thought "Instead of theoretical considerations, why not focus on capacitors that can be purchased for a project?".

    So I made up a spreadsheet of all the different types of capacitors I could find.
    The first three columns are the "type" of capacitor - example - electrolytic, solid polymer, smd.
    The next column is the minimum capacitance that I could find in that series.
    The fifth column is the maximum capacitance that I could find in that series.
    The column thereafter is the maximum voltage I could find.
    The next column is a vague representation of the cost.
    The last column (page 2 of the file) are lame comments about some of the capacitors that were noted on the web.

    I went to www.mouser.com, www.digikey.com, and www.jameco.com, and used the "highest" and "lowest" values I could find.

    The values you note may not be consistent, but they are the best I could do.

    A pdf of the spreadsheet is attached.

    My questions to the experts:
    Are there any other capacitors I've missed?
    Would you rearrange them differently?
    My guess is that the selection of capacitors by experts is something like:
    1 - Calculate the value needed for a given circuit.
    2 - Determine the maximum voltage that might hit the capacitor
    3 - Determine the size of the capacitor you might need for the circuit.
    4 - Go with the cheapest one that meets the above criteria?
    Do you all agree?

    Anything I missed?

    I thank you in advance.
    Last edited: Jan 25, 2013
  2. PGB1

    Active Member

    Jan 15, 2013
    Thank you for making & posting the pdf chart. It is handy to have.
    Personally, I'll find it useful as I learn. (And forget stuff)
  3. MrChips


    Oct 2, 2009
    No. I think you are off track in many ways.

    True, the first two electrical parameters would be capacitance and operating voltage.
    The second would be electrolytic vs non-electrolytic (polarized vs non-polarized). This is correlated with the capacitance value, physical size and cost, i.e. large values ( > 1μF are more readily available as electrolytics in a smaller package).

    More importantly, you cannot ignore the circuit design and application.

    Capacitor specifications for use in RF, timing, filter application is very different from that of a DC power supply filter application. The type of material used is important if one is looking for repeatability, reliability and temperature stability, e.g ceramic, mica, mylar, polyester, etc.

    For DC power supply and switched mode power supply, the ESR is important.
    The choice between aluminum and tantalum is important.

    For high frequency decoupling, the physical design and lead length is critical.

    Choosing the lowest cost can be detrimental in the final analysis.
  4. SPQR

    Thread Starter Member

    Nov 4, 2011
    Thanks. I too am a newbie, and whenever I find something or "create" something that might help other newbies, I try to post it.
    A lot of the stuff I've learned on this forum is not formally written in books, and is often a "pearl" from an expert who has done it 100,000 times.
    I like to collect pearls.:D

    And this is why I posted it, for comments from the experts.:)
    So other things to add to the list of considerations include:
    Aluminum vs tantalum - I hadn't seen anything on that choice.
    Polarized vs Non-polarized - I started another thread on that one a while ago
    Type of circuit - One thing I've learned here on the forum is that EVERY CIRCUIT IS DIFFERENT AND EVERY PART OF THAT CIRCUIT NEEDS TO BE CAREFULLY CONSIDERED
    ESR (equivalent series resistance) - I have seen that mentioned on the forum, but handn't thought much about it - another pearl.
    Physical Design/Lead length - frequency considerations

    So thanks VERY much for the pearls.
    I'll work some more on the list and repost it when I get a chance.