Re: gEDA-user: OFF: capacitors for RF power amplifier

[Andy Fierman <andyfierman@xxxxxxxxxxxxxxx>]

Uwe is spot on.

The capacitance vs. voltage of the X7R dielectric is not very good.
NP0/COG are usually specified for precision timing and filter
applications.

NP0/COG also have a much lower temperature coefficient.

Andy.


On 11 April 2011 15:58, Uwe Bonnes
<bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>>>>>> "Kovacs" == Kovacs Levente <leventelist@xxxxxxxxx> writes:
>
>    Kovacs> I'm currently designing a power amplifier for the HF (3-30MHz)
>    Kovacs> radio band.
>
>    Kovacs> I am selecting capacitors for the low pass harmonic filter bank
>    Kovacs> at the output.  My question is what kind of capacitors should I
>    Kovacs> use? I apply not more then 100V of say 30MHz maximum.
>
>    Kovacs> My best bet is to use X7R capacitors with as much DC voltage
>    Kovacs> rating as I can get. I don't know if there's any connection
>    Kovacs> between the DC and AC losses.
>
>
> What value do you need? Try NP0/COG type, even if substantial more
> expensive. I guess the X ceramic will introduce more harmonics than it will
> filter out...
> --
> Uwe Bonnes                bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
> --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
>
>
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