Capacitor Dielectric Classes and Their Coding

Capacitors are one of the most widely used passive electronic components, and their performance depends heavily on the dielectric material used between their plates. The dielectric not only determines the capacitance value but also defines important characteristics such as stability, tolerance, voltage rating, and temperature behaviour.

To help engineers select the right capacitor for a specific application, dielectric materials are divided into classes and often identified using standard coding systems.

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Dielectric Classes of Capacitors

The most commonly accepted classification comes from IEC and EIA standards, which define dielectric materials in terms of Class 1 and Class 2 ceramics.

1. Class 1 Dielectrics (Stable, Low Loss)

Made from materials like titanium dioxide (TiO₂).
Provide very stable capacitance with respect to temperature, frequency, and voltage.
Extremely low dielectric losses (low dissipation factor).
Used where high accuracy is required.

Examples & Coding:

1 capacitors use a letter + number + letter system that directly encodes temperature range and tolerance.

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EIA Class 1 Ceramic Capacitor Coding Table

1️⃣ First Letter – Low Temperature Coefficient

Code	Low Temp. Limit (°C)
C	–55 °C
B	–25 °C
A	0 °C

2️⃣ Digit – High Temperature Limit

Digit	High Temp. Limit (°C)
1	+45 °C
2	+65 °C
3	+85 °C
4	+125 °C
5	+155 °C

3️⃣ Second Letter – Capacitance Change (ppm/°C)

Code	Capacitance Change (ppm/°C)
A	0 ±30 ppm/°C
B	0 ±60 ppm/°C
C	0 ±90 ppm/°C
D	0 ±120 ppm/°C
E	0 ±150 ppm/°C
F	0 ±180 ppm/°C
P	+30 / –30 ppm/°C
R	+30 / –120 ppm/°C
S	+30 / –330 ppm/°C
T	+30 / –750 ppm/°C
U	+30 / –1000 ppm/°C
V	+30 / –2200 ppm/°C

✅ Example Codes

BP → –25 °C to +85 °C, 0 ±60 ppm/°C
BR → –25 °C to +85 °C, +30 / –120 ppm/°C
NP0 / C0G: Capacitance change ±30 ppm/°C (very stable, nearly ideal).
P100, N150, N750: These indicate temperature coefficients (e.g., P100 = +100 ppm/°C, N750 = -750 ppm/°C).

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Applications:

Oscillators, resonant circuits, precision filters, timing circuits.

2. Class 2 Dielectrics (High Capacitance, Less Stable)

Made from ferroelectric materials such as barium titanate.
Offer higher dielectric constants → higher capacitance in smaller sizes.
Capacitance varies more significantly with temperature, voltage, and frequency.
Higher dielectric losses compared to Class 1.

Examples & Coding:
Class 2 dielectrics use EIA coding, typically three letters:

The code has three characters:

[Low Temp Letter] [High Temp Digit] [Capacitance Change Letter]

1️⃣ First Character – Minimum Temperature Letter

Letter	Minimum Operating Temp (°C)
X	–55 °C
Y	–30 °C
Z	+10 °C

2️⃣ Second Character – Maximum Temperature Digit

Digit	Maximum Operating Temp (°C)
4	+65 °C
5	+85 °C
6	+105 °C
7	+125 °C
8	+150 °C

3️⃣ Third Character – Capacitance Change Letter

Letter	Capacitance Change Over Range
F	±7.5%
G	±10%
H	±12.5%
J	±5%
K	±10%
L	±20%
M	±20%
N	±30%
P	+10% / –10%
R	±15%
S	±22%
T	+22% / –33%
U	+22% / –56%
V	+22% / –82%

✅ Example Coding

X7R → –55 °C to +125 °C, capacitance change ±15%
Y5V → –30 °C to +85 °C, capacitance change +22% / –82%
Z5U → +10 °C to +85 °C, capacitance change +22% / –56%

Few examples can be as:

X7R: Capacitance variation ±15% from -55 °C to +125 °C
X5R: Capacitance variation ±15% from -55 °C to +85 °C
Y5V: +22% / -82% from -30 °C to +85 °C
Z5U: +22% / -56% from +10 °C to +85 °C

Applications:

Decoupling, filtering, general bypass capacitors where precision is not critical.

3. Class 3 Dielectrics (Very High Capacitance, Poor Stability)

Made with very high-permittivity materials.
Extremely high capacitance in small volumes.
Poor stability with temperature, voltage, and aging.

Examples:

Dielectrics like Y5V, Z5U fall in this category.

Applications:

Bulk decoupling, where large capacitance density matters more than precision.

Decoding the Dielectric Code

EIA standard (used mainly in ceramic capacitors) gives a three-character code:

First letter → Lowest temperature rating
Second digit → Highest temperature rating
Third letter → Capacitance variation tolerance

Common Temperature Codes:

X = -55 °C
Y = -30 °C
Z = +10 °C

Common High-Temperature Codes:

5 = +85 °C
7 = +125 °C

Common Capacitance Change Codes:

R = ±15%
S = ±22%
T = +22% / -33%
U = +22% / -56%
V = +22% / -82%

Example:

X7R → Operates -55 °C to +125 °C, capacitance change ±15%
Y5V → Operates -30 °C to +85 °C, capacitance change +22% / -82%

⚡ Summary Table

Class	Dielectric	Example Code	Capacitance Stability	Application
Class 1	NP0, C0G	NP0 / C0G	±30 ppm/°C, very stable	RF, filters, oscillators
Class 2	Ferroelectric	X7R, X5R	±15% to ±22%, moderate	Decoupling, bypass
Class 3	High-K	Y5V, Z5U	Very high variation	Bulk capacitance

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✅ Conclusion

When selecting a capacitor, understanding the dielectric class and coding is just as important as choosing the capacitance value or voltage rating.

Use Class 1 (C0G/NP0) for precision and stability.
Use Class 2 (X7R, X5R) for general-purpose decoupling and filtering.
Use Class 3 (Y5V, Z5U) where high capacitance in small space is required, but precision is not critical.

By decoding capacitor dielectric classes properly, engineers can balance cost, performance, and reliability in their designs.