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Re: parallel capacitors

Still more:

There's also the problem of spurious oscillations in the load. If all
of the stages in the load are decoupled properly, no problem. I grew up
with tubes. I remember building a "better" quality tube stabilized P/S
to drive a klystron that was noisy until I added the aforementioned
cap. Is this a transistorized P/S? Perhaps that experimentalist (white
boards) among you would check the impedance of a ten mich. cap. with an
audio osc. driven power amp. (followed by a rectifier and audio
transformer of course).

bc

Ludwik Kowalski wrote:

Jayasanker_J wrote:


Sometimes we use a big and small capacitors in parallel
for filtering purpose, for example in power supplies a 10uF
and 0,1uF. In theory, 10 and 10.1uF looks an insignificant
difference. Perhaps the small caps work better at high frequencies?


JohnD replied:

Yes. Take a look at the mfgr's spec sheets.

What kind of frequencies are important in a power supply? Not
very high, certainly below 1200 Hz in common cases. Therefore
the explanation is not satisfying. Why should 0.1uF work better
than 10 uF at f=1200 Hz? Are voltage ratings identical?