Ceramic capacitor classes and types

Ceramic capacitors are available in Class 1 or Class 2, depending on dielectric used.

Class 1 capacitors

These capacitors mostly use mainly ceramic material like TiO₂, having dielectrics with relatively low dielectric constants from 20 to 200. They generally use dielectrics like Titanium Oxide or perovskite titanate, with additives. These have low capacitance drift with temperature and voltage stability. Values of ceramic capacitors are low, from pF to few μF range. Class 1 capacitors have low losses, and are therefore used in filters and oscillators. Class 1 capacitors were once called high-frequency ceramic capacitors. They have low dielectric loss, high insulation resistance, and linear coefficient of capacitance change with temperature. These are suitable for temperature compensation, high frequency circuits etc.

Class 2 capacitors

Class 2 capacitors are made from high dielectric constant ceramics, like BaTiO₃ (barium titanate). Variations with temperature are much higher.  These have lower accuracy and stability of capacitance against voltage and temperature. They use ferroelectric ceramic dielectrics like Barium Titanate. Class 2 capacitors are used in applications like coupling or decoupling, bypassing, smoothing etc., where high tolerance on capacitance value is acceptable. These were once called low frequency ceramic capacitors. They have higher loss and lower capacitance stability compared to class 1 capacitors.

Class 3 capacitors

These use semiconductor type ceramics like Barium and strontium titanate (BaTiO₂ and SrTiO₂). These have high dielectric constants. Advantages include small size, high capacitance, high insulation resistance.

Types of Ceramic Capacitors

Ceramic capacitors are available in types like C0G (NP0), X7R, X5R, Y5V, Z5U etc. depending upon temperature characteristics. C0G and NP0 have number 0 (zero), not the letter ‘O’, which may be noted. NP0 stands for ‘Negative Positive Zero’, meaning the capacitor does not change either on positive or negative side with temperature change. Capacitance of NP0 grade capacitor has temperature coefficient of just ±0.3% from -55℃ to 125℃, or ±30 ppm/℃. This is the most stable grade of ceramic capacitors. These capacitors have a Q of over 1000, is are very stable over large frequency range.

Type C0G– C means effective number of temp. coeff. is 0. Second digit ‘0’ shows effective multiplication of temp. coeff. Is 100=1. Third letter G denotes tolerance or deviation with temperature ±30 ppm/℃.

Type code Designation

First letter of category corresponds to 55℃. Second letter indicates maximum temperature. Third letter shows change of capacitance over its temperature range.

Capacitor Type	Working Temp. Range	Capacitance change with temp.
C0G (NP0)	-55 TO 125 ℃	0-30 PPM / ℃
X7R	-55 TO 125 ℃	±15%
X6R	-55 TO 105 ℃	±22%
X5R	-55 TO 85 ℃	±15%
Y5U	-30 TO 85 ℃	+22%to -56%
Y5V	-10 TO 85 ℃	+22 to -82%
Z5U	10 TO 85 ℃	+22%to -56%
Z5V	10 TO 85 ℃	+22 to -82%

Markings on ceramic capacitors

Ceramic disc capacitors are generally printed with three-digit code to indicate its value. First two digits indicate two significant digits, while the third digit indicates number of zeroes to follow. The value thus read is in pico farads (pF). In case there is no third number, it means the value is in two digits, without any further zeroes. For example

If value printed is 27, it means 27 pF,

If 274 is the printed number, it means the value is 27 x 10⁴, or 270,000 pF, or 0.27 μF. Disc capacitors often carry a letter after the three digits, which indicates the tolerance on value. Voltage rating is usually printed, but if it is not printed, voltage rating is assumed to be 500V.

The letter code and tolerance denoted by them are given below.

	Letter	B	C	D	F	G	J	K	M	Z
Tolerance	C <10 pF ±pF	0.1	0.25	0.5	1	2
	C >10 pF ±%			0.5	1	2	5	10	20	+80-20

A ceramic disc type capacitor with code 473J printed. Capacitor value is 47 pF x 1000(3 zeros) = 47,000 pF, or 0.047 µF

Hence capacitor rating is .047 µF ± 5%

For SMD capacitors, there are two ways to mark the ratings.

1. Print the value and voltage directly on body, like 27 μF/16V
2. Follow the same system as above, used for disc capacitors, using a combination of letters and numbers.

Markings on miniature SMD ceramic capacitors are not possible on very small capacitors for want of space.

Voltage derating of ceramic capacitors

Capacitance value of most ceramic capacitors decreases with increasing applied voltage as it approaches capacitor voltage rating. This may affect operation of circuit in some cases, and more prominently in capacitors with high dielectric constant materials. A DC bias across capacitor terminals can affect its performance, and often this is taken care by keeping the voltage within a specified limit. A de-rating in voltage is used to have capacitance stability within the operating conditions. Applied voltage of capacitor cannot exceed rated voltage, and in most cases, about 70% lower voltage may be applied.