Best capacitor type for power supply decoupling?

Discussion in 'General Electronics Chat' started by fastwalker, Oct 18, 2009.

  1. fastwalker

    Thread Starter Active Member

    Jun 24, 2009
    Hi All,

    Most circuits I've come across use a .1uF capacitor across the chips for power supply decoupling. What is the best type of capacitor to use for this (e.g. ceramic, greencap, tantalum etc.)

    Thanks for any advice,
  2. Management

    Active Member

    Sep 18, 2007
  3. SgtWookie


    Jul 17, 2007
    I usually use poly film capacitors in a rectangular radial lead package. Ceramic work OK, too. Tantalum are really good, but you can get some nasty surprises (exploding caps) when powering them up after leaving them sit on a shelf for a long period of time.
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    I sometimes use both. A .1u ceramic and a 1 to 10u tantalum. In many data sheets you can find recommended vales and type for power supply decoupling. It is also important to do the decoupling correct both in respect to placement and wiring. This can be more important than the actual value used
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
    Ceramic. You can add others in parallel (tant or alum) but you need the ceramic.
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
    That is a well known failure mode of tants, not actually related to shelf aging (may get worse with age?). The ESR of a Tant is low enough that if you connect a tant to a power source with very low impedance, the surge current will blow the cap. For that reason, all our military contracts strictly wrote out the the use of solid tantalum caps. You could use wet-slug tants, because their ESR was high enough to limit the surges to a safe value.