Class 1-------------[C0G]
–Temperature compensating capacitors: have low levels of barium titanate, calcium titanate, and other things added to increase the dielectric constant, or to get a desired temperature slope.
–Very low temperature drift ,aging, voltage coefficient, frequency coefficient, leakage, and dissipation factor.
–Dielectric absorption is typically "low" but not usually specified.
–Size problem : The voltage breakdown is low
?Class 2-------------[X7R]
–Based mostly on barium titanate (Ba2 TiO3
–very poor temperature drift, high voltage-coefficient-of-capacitance and, high voltage-coefficient-of-dissipation factor, high frequency-coefficient-of-capacitance and a significant aging rate {the crystal structure}
?Class 3
–used only for DC blocking and P.S. bypassing, and even then, change in capacitance due to aging, temperature coefficient, and voltage coefficient must be taken into account.
–use the lowest K material that you can, and use them at a low percentage of rated voltage.
?Class 4 -------------[Z5U]
–the barrier-layer or reduced-titanate ceramics.
–low breakdown voltage, high leakage and all-around terrible electrical properties.
–obsolete.