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From: Michael Schwingen <news-1513678000@discworld.dascon.de>
Newsgroups: sci.electronics.design
Subject: Re: Cap C-V test
Date: 4 May 2025 16:46:05 GMT
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On 2025-05-04, john larkin <jl@glen--canyon.com> wrote:
>>
>>Not really - according to your measurements, at 25V, the caps should have
>>about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of
>>the parallel combination.
>
> One cap is .83 at 50 volts. Two in parallel would be 1.66.

> The series pair is about .73 as you note. That assumes that the DC
> voltage divides equally.

Upps, yes. Must have been lack of coffee.

> Ceramic cap nonlinearity is weird. To get the most C, is it always
> better to pick the cap with the highest nameplate capacitance?

Not sure.  In one case where I needed about 9uF at 12V DC, standard X5R/X7R
22uF/25V all came out at about 7.5uF, and 22uF/35V were not a bit better.

IIRC, X7S performed much better.

Murata Simsurfing has typical Capacitance/DC bias curves for all their parts.

cu
Michael
-- 
Some people have no respect of age unless it is bottled.