Ceramic capacitors

The choice of dielectric is largely determined by the temperature stability required:
Npo (cog) ultra stable classdielectric, with negligible dependence of electrical properties on temperature, voltage, frequency and time, used in circuits requiring stable performance.

X7r stable class =dielectric, with predictable change of properties with temperature, voltage, frequency and time. Used 5 uas blocking, coupling, by-passing and frequency discriminating elements. This dielectric is ferroelectric and offers higher capacitance ranges than class.

Y5v(z5u) general purpose class =dielectric with highest dielectric constant and greater variation of properties with temperature and test conditions. Very high capacitance per unit volume and suited for application as well as filtering,