Ceramic capacitors are broadly categorized into 4 classes based on the dielectrics used in them,
- Class 1
- Class 2
- Class 3
- Class 4
Class 3 and Class 4 capacitors are not widely used and hence have not been standardized.
Class 1 Capacitors :
Class 1 capacitors have 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
C0G
| | |
| | |– Tolerance
| |—- Multiplier
|—— Coeffcient
Look at the below table, (Source : Wikipedia)
Class 2 capacitors are specifications mentioned above are for operation within fixed temperature range of +25 degrees centigrade to +85 degrees centigrade.
Class 2 Capacitors :
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
X7R
| | |
| | |– Tolerance
| |—- Upper limit
|—— Lower limit
Refer the table below, (Source : Wikipedia)
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.
Most commonly used capacitor dielectrics are X7R,X8R,X5R,Y5V,Z5U,X7S.
Although Class 1 capacitors have more advantages than Class 2 capacitors, I encounter more X7R and X5R capacitors on day to day basis than C0G capacitors.
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