[sdiy] VCF caps in modern synths

[Neil Johnson]

Hi,

Justin Herrmann wrote:
> I think the https://passive-components.eu/dc-and-ac-bias-dependence-of-mlcc-capacitors-including-temperature-dependence/
>
> article is great, and I agree with its findings. It doesn't say anything about C0G though. It's about X5R and X7R.

Actually it does.  First it correctly identifies C0G/NP0 as Class I dielectrics:
"Dielectric materials for MLCCs come in three categories. Class I
materials (for COG and NPO parts) are very stable, but can achieve
only low εr"

And then goes on to say that they don't bother testing Class I parts
as they are known to be very stable:
"It is still the common understanding that Class I ceramics have very
little or no DC and AC bias dependence and therefore they were not
included in the study."

>From the same website, a page on Class I ceramics:
https://passive-components.eu/class-i-ceramic-dielectrics-types-performance-applications/

None of the capacitor manufacturers bother with charts of DC bias
effects on C0G/NP0 capacitors because (a) it would be a horizontal
straight line, and (b) everyone knows that C0G/NP0 capacitors are very
stable, that's why you choose them.  What you don't choose them for is
high capacitance, because the dielectric is thicker and so the
capacitance density is very low.  Fine up to a few tens on nF, but
beyond that the prices start to get silly.

Neil