Capacitor question

Is it generally safe to use ceramic caps instead of polarised tants?? Whats the difference / benefits of each??

Thanks for that Andre, i guess im looking for a more generic description. For example why would tantalum caps be better than ceramic in a simple audio amplifier?
Im still learning about electronics and diggin out generics from all the detail can be a challenge :slight_smile:

If it’s for what i think it is just use MLCC’s :wink:

@ Justin - yep it is ;). I still want to understand scenarios where one is better than the other though.

In MOST cases, ceramic caps are superior. They are typically smaller and have miniscule equivalent series resistance (ESR). Small ESR is good, while high ESR is generally bad since it means the cap wastes more power, and thus runs hotter, and is thus more likely to fail. The voltage rating of a ceramic cap is also not affected by temperature.
They are also unpolarized, so there is no wrong way to mount them. As bypass caps, they’re great.

Tantalum caps are good in that they offer very high capacitances. However, the ESR is higher, and since they are polarized, mounting them the wrong way = magic smoke gone. The biggest consideration with tantalum caps is their voltage rating. Their voltage rating drops with higher temperature, going down to as much as 50% of their rated value at higher temps. So, if you have say a tantalum cap that’s rated for 16V on paper, in practice at higher temps that cap can really only tolerate 8V. Because of this derating, when working with tantalum caps, you need to spec your max voltage by a factor of 2. For example, if you think the most your tantalum cap will see is 10V, you would be wise to spec a cap with twice that voltage rating at 20V.

However, it’s not all bad. In addition to applications where very high capacitance is needed, another application where I would use a tantalum cap is on the output stage of a linear voltage regulator. Linear regulator datasheets actually state that the output cap must have an ESR that is greater than some minimum value. If the ESR is too low, this would cause instability, so ceramic caps cannot be used.

Check ths out: Choosing between ceramic and tantalum capacitors - 31 October 2007 - Dataweek

Lots of references if you search for “ceramic vs tantalum” on Google.


@ Iggmoe - Perfect, thanks for this its exactly what i was looking for. Deserves a +1 :slight_smile:
the other reason i wnated to check was that this thing im working on may have to have 0402 size caps and im a guaranteed to put them on in the genie releasing direction :slight_smile:

This reference is pretty good, too. Especially the table at the end:$file/2008-11%20Update%20-%20Ceramic%20versus%20Tantalum.pdf

If you go with MLCC, note that the capacitance can change vs temperature. How stable the capacitance is over time and temperature is indicated by a code such as X7R or Y5V. For applications where having a tight and stable capacitance value is critical, I would go with X7R or better. An explanation of these codes can be found here:$file/F3101_CerPerChar.pdf

@ iggmoe - Cool, looks like i made a good choice on X5R then :slight_smile: