Electrolytic vs. Tantalum @ Low Voltage

Hi,

I need a cap that works (maintains its value reasonably) all the way down to potentially 70mV (I know, I know). Since electrolytics won't do this, I was wondering if tantalums would? If not how bad are they? Thanks!

speakerguy79 said:

Hi,

I need a cap that works (maintains its value reasonably) all the way down to potentially 70mV (I know, I know). Since electrolytics won't do this, I was wondering if tantalums would? If not how bad are they? Thanks!

Click to expand...

Can you quantify "maintains its value reasonably" ?

Does it have to be electrolytic? Can you consider Film types that have low DA & low voltage coeficient?

Just use tantalums if the capacitance is available, the voltage you are using is 50% or less than the rated voltage, and it's reasonably priced. What frequency did you need it at?

+/- 50% tolerance would be fine I think since this is only a filter cap. Frequency is in the tens of kHz. Value needs to be a few hundred uF and it has to be small. The value and size kills everything else I think. I'm trying to find a way to do this with a reasonable bias voltage on the cap but haven't come up with one yet. If I do then aluminum electrolytics will do fine I think. I will have a bias voltage of at least 1 and maybe as much as 3.3 or 5 volts hopefully.

Thanks guys,


Mark

Yeah...you aren't going to get a few 100s of uF tantalums at a reasonable cost. Nope nope. About $8 per 470uF cap.

what exactly you trying todo and what capacitance do you think you need? 70mV sounds more like a signal potential rather then a rail potiential