[R-390] CAPACITOR FIGHT

[Charles Steinmetz]

Dave wrote:

>I tried to calculate the reliability of film/foil vs. ceramic for 
>C553 and got unclear results

There are other important factors to consider besides 
reliability.  Unless the ceramic is type C0G (NP0), the voltage 
coefficient of capacitance, dielectric absorption, and dissipation 
factor can cause unwanted distortion in the IF.  0.01uF, 1000v C0G 
caps are available (e.g., AVX SV01AA103JAA), so this is an option.

Maybe it's just tradition, but I think I'd still rather use a film-and-foil.

>I also simulated a metalized-film self-heal event in SPICE, and got 
>an 80mA current peak that lasted 10us.  I don't think this will heat 
>the wire enough to fuse it, but who wants to test it when film/foils 
>are still readily available?

80mA is a lot of current for the tiny wire in a mechanical filter 
drive coil.  Also, once a metalized film cap starts having 
self-healing events, they tend to become more and more frequent.  No, thanks!

Best regards,

Charles