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From: john larkin <jl@glen--canyon.com>
Newsgroups: sci.electronics.design
Subject: Re: strange cap
Date: Thu, 10 Jul 2025 08:00:26 -0700
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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