Ceramic capacitors are broadly categorized into 4 classes based on the dielectrics used in them. There are four classes of Ceramic Capacitors. Class 3 and Class 4 capacitors are not widely and have not been standardized, therefore we will be looking today at the differences in Class 1 and Class 2.
Class 1 Capacitors have the following characteristics,
- Linear temperature coefficient : Their capacitance varies linearly with temperature
- No Voltage dependency : Their capacitance does not depend on the applied voltage
- No Aging : They do not suffer significant aging process due to para electric materials used in manufacturing
- No electrical losses : Have significantly low electrical losses compared to Class 2 capacitors
- Used in High Q filters : Due to the above properties they are used in applications like resonant circuits, PLL and Oscillators.
-
Have high stability and accuracy
They use a 3 digit notation to indicate the dielectric used in them according to EIA RS-198 standard.
Example C0G
Class 1 capacitors are specifications mentioned above are for operation within fixed temperature range of +25 degrees centigrade to +85 degrees centigrade.
Class 2 capacitors have following characteristics
- Non-Linear temperature coefficient : Their capacitance varies non linearly with temperature
- High Voltage dependency : Their capacitance highly depends on the applied voltage
- Suffer Aging : They suffer significant aging process due to ferro electric materials used in manufacturing
- High electrical losses : Have significantly high electrical losses compared to Class 1 capacitors
- High Permittvity : Due to high Permittivity they have high volumetric efficiency
- High Capacitance values : Due to high Permittivity large capacitance values can be achieved in small device casings like 0201, 0402, 0603
- Used in smoothing applications : Due to the above properties they are used in applications like bypassing, coupling, decoupling.
- Have low stability and accuracy
They use a 3 digit notation to indicate the dielectric used in them according to EIA RS-198 standard
Example X7R
So according to the above table,
When manufacturer says that this is a X7R capacitor, it means that the capacitor can operate from – 55 degrees centigrade to + 125 degrees centigrade temperature and the capacitance of the capacitor will not vary more or less than 15% from its nominal value specified.
Similarly, When manufacturer says that this is a Y5V capacitor, it means that the capacitor can operate from -30 degrees centigrade to +85 degrees centigrade temperature and the capacitance of the capacitor will not increase more than 22% and not decrease below 82% from its nominal value.