Re: strange cap

On Thu, 10 Jul 2025 01:52:42 -0000 (UTC), Sergey Kubushyn
<ksi@koi8.net> wrote:

john larkin <jl@glen--canyon.com> wrote:

https://www.mouser.com/ProductDetail/KEMET/CKC33C224KDGLCTU?qs=sGAEpiMZZMvsSlwiRhF8qtsGU%2FCnaNeQZfloC%2Fa%2FQTldKZA3leWJsw%3D%3D
 
$27 each. I think I'll use film.

>
Nothing strange, just a relatively big stacked HIGH VOLTAGE and [relatively]
HIGH CAPACITANCE (at least for such voltage rating) _C0G_ ceramic capacitor.
The interesting thing is that it is sintered into a relatively small almost
monolithic block that can be installed two ways. Earlier such stacked
capacitors were made by soldering several separate caps to flat bus bar like
leads with a high temperature solder. That was adding inductance and didn't
allow the "Low Loss" mounting as it is shown in the datasheet for this one.
They also were mostly thruhole parts, with several pins on those bus bar
leads for soldering into TH pads.
>
No wonder it is THAT expensive -- it is not a jellybean part that cost a
dollar per bucket and you put them all over left and right...
>
A comparable film capacitor will be bigger and will have significantly
poorer ESL and ESR.

ESL for sure. Ceramics and self-healing films can have considerable
ESR too.

Of course I'd parallel a couple big leaded film caps with a few
surface-mount ceramics.

I can get 1 uF at 1KV in a film cap for well under $2.

This is for a 750 volt into 50-ohm pulser with, optimistically, under
1 ns edges.

We could even use polymer electrolytics in series to get the voltage.
We'd get lots of C. ESR and ESL are impressive on polymers.

https://www.dropbox.com/scl/fi/bvx38d23enwxx20tv7rgw/Kemet_A765EB187M0JLAE020_TDR.jpg?rlkey=7ieq6ughiij6twxreej7ooeq9&raw=1

https://www.dropbox.com/scl/fi/215r24f5wfjcrupr2d32w/KEMET_A765EB187M0JLAE020_ESR_100mA_.png?rlkey=g03gvzne50ov1f01fhiyleccp&raw=1