[sdiy] Hand-matching capacitors for filter stages

[jays at aracnet.com]

All,

At one point I was looking at doing a SMD VCO. So I looked into SMD solutions for the timing cap. There were a number of low value (pfs) NPO/COG ceramic caps that were 1.0% (and maybe even 0.1%, can't remember). Some even had better specs that the poly caps. The price is pretty steep though, $2 or more.

Jay S.


Ian Fritz wrote:

> At 02:36 PM 2/9/2010, Andre Majorel wrote:
> >On 2010-02-09 11:10 -0800, thx1138 wrote:
> >
> > > I can tell you that Ceramic and Electrolytic Caps are a real NO
> > > due to cap value changing over time and temp.
> >
> >But *what* ceramic caps ? Z5U or C0G/NP0 ? The latter look pretty
> >good and I think someone on the list had success using them in
> >place of polystyrene.
> 
> Absolutely!  I have tested NP0 quite carefully vs polystyrene in precision 
> VCOs and can see no noticable difference.  Specifically, no readjustment of 
> tracking or of the HF tracking correction was needed.
> 
> I've stayed away from silver mica's because in general they are said to 
> have significant soakage effects.
> 
> Ian 
> 
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