A circuit design calls for capacitors for power-supply decoupling. An engineer specifies 10 µF ceramic capacitors without considering the dielectric type, only to find the circuit behaves unreliably under extreme temperatures. Measurements show capacitance has drifted far from its rated value, resulting in insufficient filtering under operating conditions.
The root cause: general-purpose Class 2 ceramic capacitors were selected, while temperature-stable Class 1 dielectrics were actually needed. This represents a common yet avoidable design mistake. Understanding ceramic capacitor types and their key characteristics supports well-informed component selection, balancing performance, cost, and long-term reliability.
Understanding Ceramic Capacitors
What Are Ceramic Capacitors?
Ceramic capacitors employ ceramic material as their dielectric layer, which is sandwiched between metallic electrodes to store electrical charge. The dominant modern form is the multilayer ceramic capacitor (MLCC): numerous thin ceramic layers are stacked in parallel and internally interconnected to deliver high capacitance within compact component packages.
Ceramic capacitors account for roughly 60 % of total capacitor production, driven mainly by cost-effectiveness, small footprint, and high volumetric capacitance density. Even so, the term “ceramic capacitor” covers several fundamentally different families, each with unique characteristics and application suitability.
Why Ceramic Type Matters
Not all ceramic capacitors perform the same. Class 1 dielectrics deliver highly stable capacitance over wide temperature ranges. Class 2 dielectrics offer much higher capacitance density but suffer from capacitance shifts caused by temperature change and applied operating voltage. Choosing an unsuitable dielectric type for a given application can lead to insufficient performance, field-site failures, or unnecessary costs.
Ceramic Dielectric Materials
Ferroelectric Ceramics
Many ceramic capacitors (primarily Class 2 types) employ ferroelectric materials — ceramics exhibiting strong electrical polarization that delivers far higher capacitance than non ferroelectric dielectrics. These materials become polarized under applied electric fields, forming electric dipoles for charge storage. By contrast, Class 1 temperature stable ceramic dielectrics are non ferroelectric, trading high permittivity for minimal capacitance drift.
Relative permittivity for ferroelectric ceramic formulations typically spans 100 to 10 000 and above. For comparison: mica (~6), polymer film dielectrics (2 4), and vacuum (1). This high dielectric constant is what enables high capacitance density within small component footprints.
Composition and Properties
Ceramic dielectrics are complex metal-oxide systems, most commonly barium titanate-based formulations, blended with dopant additives to tune electrical performance. Material composition governs these key characteristics:
- Dielectric constant:Higher values yield higher volumetric capacitance density
- Temperature coefficient:How much capacitance changes with temperature
- Loss factor:Dissipation and heat generation
- Breakdown strength:Maximum voltage-withstand capability
Class 1 Ceramic Capacitors: Stable Type
C0G/NP0 Definition
Class 1 ceramics, primarily designated as C0G (EIA standard; NP0 is the historical MIL-STD equivalent), deliver near-zero temperature coefficient of capacitance. A C0G capacitor features a temperature coefficient of ±30 ppm/°C (parts per million per degree Celsius), with total capacitance change limited to max ±0.3 % across the −55 °C to +125 °C operating range.
For example, a 100 nF C0G capacitor holds nearly constant capacitance over the full operating-temperature span. Unlike Class 2 dielectrics, it suffers almost no ferroelectric-related aging and negligible capacitance shift under applied DC bias.
Characteristics
| Characteristic | C0G/NP0 Class 1 |
| Temperature Coefficient | ±30 ppm/°C (max ±0.3 % across full temperature range) |
| Dissipation Factor | Typically <0.1 % |
| Voltage Derating | Minimal voltage-dependent change |
| Aging | Negligible; virtually no ferroelectric aging (<1 % over 10 years) |
| Frequency Dependence | Excellent stability across frequency |
| Capacitance Density | Lower than Class 2 |
| Cost | Higher than Class 2 |
Applications
Class 1 ceramics are appropriate for:
- Precision timing circuits where frequency stability is critical
- Resonant networks in RF circuits
- Measurement instruments requiring stable reference capacitance
- Military/aerospace applications with strict reliability requirements
- Long-term stable filtering where aging is unacceptable
Class 2 Ceramic Capacitors: General Purpose Type
X7R and X5R Properties
Class 2 ceramics provide much higher capacitance density than Class 1 but exhibit temperature-dependent behavior. X7R ceramics, the most common Class 2 type, maintain capacitance within ±15% from -55°C to +125°C — a much wider change than C0G but acceptable for many applications.
X5R ceramics specify a narrower temperature range (-55°C to +85°C) but with the same ±15% tolerance, offering cost advantages in applications not requiring full military temperature range.
Voltage and Temperature Derating
Class 2 capacitors suffer DC-bias-dependent capacitance reduction: effective capacitance drops as applied DC voltage rises. The magnitude of this drop varies strongly with capacitance value, dielectric thickness, and component footprint. High-value MLCC can experience very large capacitance loss when operated near their rated voltage. Consequently, real-world operating capacitance can deviate significantly from the zero-bias rated datasheet value.
| Property | X7R Class 2 |
| Temperature Coefficient | ±15% (-55°C to +125°C) |
| DC–Bias–Induced Capacitance Shift | Highly variable; depends on capacitance, footprint and applied voltage |
| Dissipation Factor | Typically 2-5% |
| Aging | 2-4% first year, then stabilizes |
| Frequency Dependence | Capacitance changes with frequency |
| Capacitance Density | High (compact size) |
| Cost | Lower than Class 1 |
Aging Mechanism
A key characteristic of Class 2 ferroelectric ceramics is aging: gradual capacitance loss over elapsed time. Aging follows a logarithmic time-dependent curve: roughly 2-4 % capacitance loss occurs within the first year, after which the drift rate becomes much slower. Elevated operating temperatures accelerate aging effects.
Important note: Aging is physically reversible by heating the component above its Curie temperature (~125 °C) to reset ferroelectric domain alignment. However, this reset is generally impractical inside finished end-equipment, so aging*induced drift must be treated as effectively permanent for system-level operation.
For systems requiring stable capacitance over multi-year service life, designers must compensate for aging, temperature and DC-bias drift by selecting a higher initial capacitance value, so that capacitance remains above minimum required levels at end-of-life.
Class 1 vs Class 2: Comparison
| Aspect | Class 1 (C0G) | Class 2 (X7R) |
| Stability | Excellent | Good |
| Temperature Change | ±0.3% | ±15% |
| Voltage Dependence | Minimal | Significant; highly dependent on value, footprint and applied DC bias |
| Aging | Negligible | 2-4 % capacitance loss within first year |
| Dissipation Factor | Typically <0.1 % | 2-5% |
| Capacitance Density | Lower | Higher |
| Cost | Higher | Lower |
| Suitable For | Precision timing, RF, reference circuits | General-purpose decoupling, power-supply filtering |
Other Ceramic Types
Y5V and Z5U are Class 2 ceramic dielectrics featuring very high capacitance density but large, asymmetric capacitance shifts across temperature.
– Z5U: operates from +10 °C to +85 °C with capacitance variation of +22 % / −56 %
–Y5V: operates from −30 °C to +85 °C with capacitance variation of +22 % / −82 %
Both types exhibit severe DC-bias-induced capacitance reduction. They deliver cost benefits for cost-sensitive applications that can tolerate substantial capacitance drift over operating conditions.
High-voltage ceramics employ specialized structures (stacked, tubular, disk-form) to reach voltage ratings of 1 kV and above. These components require extra design attention to reliability, electric-field stress, and thermal management.
Selecting Ceramic Capacitor Type
For Precision Applications
Use Class 1 (C0G) when capacitance stability is critical:
- Timing circuits and oscillators
- Resonant networks
- Precision measurement equipment
- Filter networks requiring stable frequency response
For General-Purpose Decoupling and Bypass
Class 2 (X7R) is typically adequate and more cost-effective:
- Power supply decoupling
- High-frequency bypass
- General filtering applications where capacitance variation is acceptable
For Cost-Sensitive Applications
Y5V or Z5U ceramics minimize cost at the expense of capacitance stability. These types are appropriate when the capacitive effects on circuit operation are minimal.
Conclusion
Ceramic capacitors are offered in multiple dielectric families with fundamentally different electrical characteristics. Class 1 (C0G/NP0) ceramics deliver temperature-stable capacitance, well-suited for precision circuits and use-cases where consistent capacitance performance is critical. Class 2 (X7R/X5R) ceramics feature higher capacitance density and lower cost, yet suffer capacitance shifts driven by temperature and applied DC voltage.
Appropriate part selection aligned with application requirements optimizes performance, long-term reliability, and overall system cost. A solid grasp of ceramic dielectric characteristics supports well-informed component choices, helps avoid common design pitfalls, and guarantees reliable operation across varying temperature and operating conditions.
Frequently Asked Questions
Q: Why would I use C0G capacitors if X7R is cheaper? C0G provides stable capacitance across temperature, essential for precision circuits. X7R’s ±15% change would degrade circuit performance in timing or resonant applications. Use C0G only where stability is necessary; X7R everywhere else to minimize cost.
Q: How much does ceramic capacitor aging matter? For short-term applications (hours to days), aging is negligible. For equipment operating years, aging can reduce capacitance by 2-4% or more. Designs should specify capacitance 5-10% higher than minimum required, allowing aging margin during service life.
Q: Does applied voltage really change capacitance? Yes, significantly in Class 2 ceramics. The magnitude of capacitance reduction depends on component value, footprint and applied DC bias. Real-world operating capacitance can be substantially lower than the zero-bias datasheet rating. Designs must account for this effect to guarantee sufficient filtering or coupling under actual operating conditions.
Q: Can I substitute X7R for C0G if cost is critical? Only if the circuit tolerates capacitance change. If capacitance variation affects circuit operation (timing frequency, resonance frequency, filter response), C0G is necessary. If not, X7R cost savings are significant.
Q: What does dissipation factor mean and why does it matter? Dissipation factor describes losses in the capacitor. A 5% dissipation factor means 5% of stored energy is dissipated as heat. At high frequencies or with high ripple currents, dissipation generates significant heat. Class 2 ceramics (higher dissipation) can overheat in demanding applications; Class 1 generates less heat.
Next Steps
To systematically evaluate and select the appropriate ceramic capacitor types for your application, contact LCA’s capacitor application specialists for a Class 1 vs Class 2 comparison table, temperature and voltage derating curves, capacitance change calculation methodology, aging compensation guidelines, application selection flowchart, and design checklist.
Technical guidance in this article reflects general ceramic capacitor characteristics and selection principles. Specific requirements depend on your temperature range, frequency of operation, stability requirements, and application. Always verify component specifications against manufacturer datasheets and conduct appropriate testing before production commitment.
