Hi

Can an infinite impedance in a parallel LC circuit be achieved using resonance frequency with a bi-polar capacitor? or does it have to be a NP capacitor?

i.e. if a diode is installed "in series with the capacitor" Cathode end to + capacitor, will that change the characteristics regarding the effect of the frequency? if so, how else can the task be achieved?

Thanks

 

Can an infinite impedance in a parallel LC circuit be achieved

If you can obtain a perfect inductor and a perfect capacitor plus perfect wire, perhaps. That the capacitor is non-polar or bipolar is not significant. Those perfect components are hard to find outside of academic settings (specifically, textbooks), though.

The diode will not affect the frequency (how could it?), but it will make the charging current to the capacitor unipolar. The capacitor will charge in one polarity only, which will have a negative effect on resonance. The parallel resonance effect depends on the fact that both components will have opposing and mutually canceling responses at resonance - the capacitor will hold its charge and not be able to "act" resonantly.

You might review the relevant material in our Ebook - http://www.allaboutcircuits.com/vol_2/chpt_6/6.html