I don't recall the specifics of polypropylene, but in mylar the metallized film is preferred in line V applications because the arc in local breakdown in the dielectric can "clear" by eroding the thin metallization in the vicinity of the arc
with foil electrodes a dielectric breakdown, not limited by external impedance, will destroy the Cap
in fact , some "metallized film" polypropylene use double sided metallized mylar as the electrodes
for low esr and high SRF you really want "extended foil" construction where the foil edges are shorted by endcaps/spray metallization/ultrasonic welding
with foil electrodes a dielectric breakdown, not limited by external impedance, will destroy the Cap
in fact , some "metallized film" polypropylene use double sided metallized mylar as the electrodes
for low esr and high SRF you really want "extended foil" construction where the foil edges are shorted by endcaps/spray metallization/ultrasonic welding
More curiosity. Would the 'islandy' nature of the film mimic DA?
I think the poor conductivity of the coating on CRTs causes them to 'recover' a charge after shorting them out. I always thought the discharge causes a voltage gradient around the anode connection because of the resistance caused slow discharge. The 'recovery' is just the charge migrating through the high resistance coating to equalize the charge. Doesn't this mimic DA?
G²
Resistance, either internal or external, is not the same as DA. Distortion analysis will reveal the difference. Internal resistance would add to external resistance and alter the RC time constant of whatever circuit is being used. DA would still be the same.
No. It's a pure resistance and a damn small one. With a high DA, you can charge up a cap, discharge it, then open circuit it, and you'll see voltage build back up- memory, as it were. It's mostly a function of dielectric. ESR is just a simple resistance, on the order of milliohms.
DA in itself is a linear phenomenon, and doesn't cause distortion.
It is true however that dielectrics having a high DA often happen to be non-linear, but that's incidental and another story.
Probably not, but I was just correcting the assertion that "distortion in capacitors is caused by DA".
The effect is to alter the phase and frequency responses.
But this effect has to be put in perspective too: it can only manifest itself where the capacitor is used as a reactive element, which is not the case in coupling or bypassing applications, that is over 90% of capacitors in audio.
In filters, it does matter, but in general, the effect will be very small compared to the "normal" filtering action of the network, and even in high Q active filters, it is normally sufficient to simply include it in the generic losses, the tan delta.
It does a bit of both, short term and long term.
External vibration. self excited vibration, wire to foil connection contamination, moisture contamination, changes in value due to applied voltage, tribo electric effect, and of course the best known external fields the outside foil.
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