Re: gEDA-user: ESR of 2.2u ceramic capacitor

[sdb@xxxxxxxxxx (Stuart Brorson)]

> > Ohmic resistance of ceramics is usually very small (the electrodes  
> > are metal), but high K ceramic dielectrics generally have a lot of  
> > hysteresis, which can be trouble in some applications.
> 
> What does it mean? That the capacitor loses capacity when switching
> between charge and discharge? Like riding a snowboard with loose boots
> and switching edges?

Capacitors can be non-linear, meaning that the capacitance can depend
upon the applied voltage.  Worse, the capacitance can depend upon the
*history* of the applied voltage.

For some applications (e.g. decoupling), this isn't a problem.
However, for high-quality audio circuits  & filters, capacitor
nonlinearity can be a problem.  The best linear caps are the
polypropylene & (for small values small values) NPO ceramic.   On the
other hand, ceramic X7R is nonlinear.  Electrolytic caps are
really nasty when it comes to their signal carrying properties.  They
are best used as decoupling caps, and not used otherwise.

Here's a section from the Wikipeda about capacitor non-idealities:

http://en.wikipedia.org/wiki/Practical_capacitors#Non-idealities_of_practical_capacitors

Stuart