Trying to understand tantalum capacitors



  • Can anyone explain me this capacitance equation C=Q/V in simple terms? I was trying to understand here https://www.derf.com/how-tantalum-capacitors-work/ but didn't get any success so decided to take help through forum. Looking forward to reply soon.

    Thanks



  • Try to Google on "capacitor water analogy", that makes it more clear I guess. Or do you mean tantalum capacitors specifically?



  • @Alwyn Don't bother with tantalum capacitors. They have an annoying tendancy to fail as a short circuit. Better to use ceramic capacitors for compact builds or electrolytic ones where space is available.

    And always try to use a capacitor at the next highest voltage rating to the highest one in your circuit as higher voltage ones often loose capacitance when used
    at lower voltages. So for 5V supply, use 6.3V or just above, but if you use 50V or 220V then capcaitance will most likely be degraded if used at 5V.



  • Couple of things to think about with capacitors.

    With electrolytic caps there ESR ( Equivalent Series Resistance) is quite high if you need a lower ESR try going for a polymer electrolytic.

    Ceramic capacitors, as previously said don’t go for a capacitor that is rated at the same voltage, in my experience at least 1.5 to 3 times the max voltage your working with. So if your working with 5V I would go with a 16V part.

    The reason for this is the DC BIAS of ceramic capacitors, if you need 1uF of capacitance and use a 6.3V cap the DC BIAS of the capacitor could only 20% to 30% of the stated capacitance. Therefore you would need 3 or 4 capacitors at 6.3V to get the correct capacitance where as with a 16V part you may only need 2 capacitors in parallel to achieve the correct capacitance.

    Most good capacitor manufactures will have these online in the specifications area of there website.

    Also be careful depending on the power supply your using they may need electrolytic as the ESR of ceramics is very low and this can cause the power supply to become unstable as the control loop of the power supply can’t cope.

    These are lessons learned over the years as I alway say you learn more from making a mistake than being told what to do and getting it correct 100% of the time.


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