[Open_electroporator] why your 4.7uF ceramic cap acts like a 0.33uF cap...

John Griessen john at cibolo.com
Fri Feb 24 01:55:15 UTC 2017


On 02/23/2017 07:13 PM, Nathan McCorkle wrote:
>
> This seems like it could be relevant to the board BOM choices... hopefully the image/diagram embedded gets forwarded

I've been doing the purchasing agent legwork on this some recently.  Just got this back from China:

On 02/23/2017 04:48 AM, monica wrote:
 > Dear John,
 >
 >
 >
 > We have receive your mail.
 >
 >
 >
 > We think you should be misunderstood.
 >
 > Although 10pcs sample test is ok, but DC-BIAS in the industry should no suppliers will guarantee this one,
 >
 > Please note.
 >
 >
 >
 > If your application case about the capacitance of the choice of MLCC, we suggest you use Electrolytic capacitor
 >
 > Or Tantalum capacitor instead of MLCC, capacitance decay will not be due to voltage.
 >
 >
 >
 > Please take a little time to read the file, maybe you can found more information.
 >


What file does she refer to?  --->>> 
http://www.edn.com/design/analog/4402049/2/Temperature-and-voltage-variation-of-ceramic-capacitors--or-why-your-4-7--F-capacitor-becomes-a-0-33--F-capacitor

I think some MLCC makers  might specify capacity with DC bias, but not certain any that do will cost less.
Samsung has fairly decent descriptions of their DC bias, but very separate from specs.

Maybe when I ask them, they will say like Monica of supertech.tw says, "Although 10pcs sample test is ok, but DC-BIAS in the 
industry should no suppliers will guarantee this one,
 >
 > Please note."

:-)

There is probably no cheap tiny cap except that Aluminum caps have gotten much better, and come in semi-tiny sizes now...

There may be a supplier that grades them as LEDs have been done and sells the "guaranteed performance ones for more money.

Have not found them yet.  Will do aluminum in the meanwhile.


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