I've been using Murata's GRM series capacitors with X7R dielectric for power supply bypassing in digital circuits and am now looking into using the same capacitors in a Sallen-Key bandpass filter for audio signals.
The TI application report "Analysis of the Sallen-Key Architecture" suggest using NP0 and avoiding Z5U while stating "X7R is OK in a pinch". If I understand the matter correctly, the X75 and Z5U are worse than NP0/C0G when it comes to aging, stability of capacitance over temperature and changes of capacitance depending on applied voltage since the X75 and Z5U are ferroelectric.
The last one is supposed to make X75 and Z5U a bad idea for audio circuitry sice they will add "a lot" of distortion to the signal (I've seen a diagram showing 100 times the TDH when measured against C0G in a simple RC highpass).
So my questions are :
Is the a recommended book that covers these details of ceramic capacitors (physics and chemistry of the dielectric and the effect on component behaviour)?
What effect is responsible for the distortion of a sine wave applied to or passing through a capacitor ? Is it only the change of capacitance with voltage ? Again, is there a recommended book that covers this ?
How can the adding of distortion be modeled in e.g. LTSpice - the default capacitor model only covers ESR,ESI,EPR and EPC ?
any hints appreciated,
Chris