So many type of capacitors!

Discussion in 'General Electronics Chat' started by Sonoma_Dog, Sep 16, 2008.

  1. Sonoma_Dog

    Thread Starter Active Member

    Jul 24, 2008
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    I needed some bypass capacitors to filter out the noise for a 5 volt regulator.
    The datasheet recommenced to use a .33uf on the input and 0.1uf on the output. Then i was doing some parts research and found out there are a lot of different types of capacitors.

    Which type of capacitor is best for bypass. and anyone have a useful like that talks about the pros and cons of different types of capacitor

    Here are some different type they have available
    Aluminum Electrolytic
    Ceramic Disc & Plate
    Ceramic Multi-Layer
    Double Layer
    Film
    Silver Mica
    Tantalum&Niobium Oxide
    and
    Trimmer / Variable

    Thanks!!
     
    Last edited: Sep 16, 2008
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    I'm going to be a weenie and point you at this site - http://www.radio-electronics.com/info/data/capacitor/capacitor_types.php.

    For your regulator, use an electrolytic on the input. The capacity should be selected for the amount of current expected, but they are cheap - get something with twice the voltage rating as the actual input voltage, and figure that anything over 22 uF is probably good (I tend to select by rule of thumb).

    The output needs something with lower ESR, so one or two .1 uF ceramic types would be good.
     
  3. Audioguru

    New Member

    Dec 20, 2007
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    896
    National Semi says to use a 0.1uF ceramic disc capacitor at the output of an LM78xx regulator because it is very good at high frequencies.
    They say to use a 1uF to 1000uF electrolytic capacitor at the output of an LM317 regulator.
    The 0.33uF input capacitor can be any type and is needed only if the main power supply filter capacitor is more than a few inches away.

    Low dropout regulators are different. Their datasheet says the range of ESR of their fairly high value output capacitor is acceptable. They oscillate without an appropriate output capacitor.
     
  4. Sonoma_Dog

    Thread Starter Active Member

    Jul 24, 2008
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    0
    it was a very helpful article, I now sort of understand the different type of caps.
    and other question arise, I was looking for caps on the a website, and it seems like the 0.1uf cap is more expensive then the 22uf.

    So i am wondering if i can use 22uf on both side (input and output).
    since the bigger capacity it have the better filtering it will be.

    and what is ESR ?

    Thakns!
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    What is the part number of your regulator IC?
    Which type of 0.22uf capacitor are you planning to use?
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    ESR is Effective Series Resistance. It has to do with the characteristic of a capacitor that makes it less effective when used as a filter for a high frequency, like the output od a SMPS. Caps with high ESR can get hot and explode.

    A garden variety .1 uF ceramic with a Z5U tolerance should cost on the order of $.20. That's pretty sloppy as to actual value. A .1 uF film with a 2% tolerance will cost a couple of bucks.
     
  7. SIcam

    Active Member

    Aug 9, 2008
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    Sparkfun.com, " My recommendation: just use a couple basic caps 100uF (one-hundred micro farad) on the input and 10uF on the output. You will use a lot of 100uF and 10uF around power systems and you will eat 0.1uF (point one micro farad) caps like candy around micros."
     
  8. bertus

    Administrator

    Apr 5, 2008
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  9. Sonoma_Dog

    Thread Starter Active Member

    Jul 24, 2008
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    0
    This is the regulator i am going to use (link 1) and in the datasheet it says to use a .33uf on the input and .1uf on the output.

    Link 2 and link 3 are the cap i am planing to use.

    I will have to spend time to read some more article, since i dont have a solid understanding of capacitor. It's stupid i didn't learn any of these from college.

    link 1: http://www.newark.com/jsp/search/productdetail.jsp?sku=89K1377
    link 2: http://www.newark.com/jsp/search/productdetail.jsp?sku=70K9690
    link 3: http://www.newark.com/jsp/search/productdetail.jsp?sku=97M4046

    Thank you for all your help tho!
     
  10. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    The 0.33 uf capacitor at the input and the 0.1 uf capacitor at the output are used to prvent the regulator IC from oscillating.
    They should be mounted close to the regulator.
    Best is to take ceramic or "stabitat" capacitors for it.

    Greetings,
    Bertus
     
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