Re: Cap C-V test

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.