Capacitor Guide

Understanding Capacitor Dielectrics

Learn how capacitor dielectric types affect capacitance stability, voltage behavior, ESR, aging, temperature performance, and application suitability.

Reading Time: 13 min
Difficulty: Intermediate
Last Updated: July 15, 2026

Introduction

Dielectric material is one of the biggest reasons two capacitors with the same nominal capacitance can behave very differently. A 100 nF C0G capacitor, a 100 nF X7R capacitor, and a 100 nF Y5V capacitor may all share the same printed value, but they do not offer the same stability, voltage behavior, aging, size, or cost.

The dielectric affects capacitance density, temperature coefficient, DC bias loss, ESR, leakage, dielectric absorption, lifetime, and frequency behavior. For real design work, capacitance is only the starting point. The correct dielectric is what makes the capacitor suitable for timing, filtering, decoupling, energy storage, RF, audio, or pulse applications.

What Is a Capacitor Dielectric?

A capacitor stores energy in an electric field between conductive plates. The dielectric is the insulating material between those plates. Materials with higher relative permittivity can produce more capacitance in a smaller volume, but high capacitance density often comes with tradeoffs in stability, voltage coefficient, aging, and loss.

The dielectric sits between conductive plates. Its material properties influence capacitance density, stability, voltage behavior, ESR, aging, leakage, and frequency performance.

Key Properties Engineers Should Compare

Capacitance stability

How much capacitance changes with temperature, voltage, time, and frequency.

Temperature coefficient

How capacitance changes across the operating temperature range.

Voltage coefficient

How capacitance changes under DC bias or AC voltage swing.

Aging

How capacitance changes over time after manufacture or heat exposure.

ESR and losses

How much resistance and heat appear at operating frequency and ripple current.

Leakage and polarity

Whether the part leaks current, has polarity, or needs voltage derating.

Ceramic Capacitor Classes

Class 1: C0G / NP0

C0G/NP0 is the stable ceramic choice. It has low loss, negligible aging, and very small capacitance change with voltage. It is excellent for RF, oscillators, precision filters, and timing networks, but capacitance density is limited.

Class 2: X7R and X5R

X7R and X5R provide much higher capacitance density and are common in MLCC decoupling. They are practical for power rails, but capacitance can fall with DC bias and change with time.

Low-stability ceramics: Y5V and Z5U

Y5V and Z5U can show high apparent capacitance in small packages, but temperature, voltage, and aging effects are large. They are best reserved for noncritical bypassing.

C0G / NP0

Stability: Very high stability, about 0 ±30 ppm/°C

Voltage behavior: Very low capacitance change with DC bias

ESR: Very low ESR at high frequency

Applications: RF networks, Oscillators, Filters, Timing circuits, Precision analog circuits.

X7R

Stability: ±15% from -55°C to 125°C

Voltage behavior: Capacitance can decrease significantly with DC bias

ESR: Low ESR, suitable for decoupling

Applications: Power rail decoupling, Bypass capacitors, General filtering, Bulk ceramic capacitance.

X5R

Stability: ±15% from -55°C to 85°C

Voltage behavior: Strong capacitance reduction with DC bias, especially in small packages

ESR: Low ESR

Applications: Portable electronics, Digital decoupling, Low-voltage power rails, Compact filters.

Y5V

Stability: +22% / -82% from -30°C to 85°C

Voltage behavior: Very large capacitance loss with DC bias

ESR: Low ESR, but capacitance stability is poor

Applications: Noncritical bypassing, Low-cost consumer circuits, Loose filtering requirements.

Z5U

Stability: +22% / -56% from 10°C to 85°C

Voltage behavior: Large capacitance change with DC bias

ESR: Low ESR for ceramic construction

Applications: Noncritical decoupling, Consumer bypass capacitors, Loose-tolerance filtering.

Film Capacitors

Stability: Good to excellent depending on film material

Voltage behavior: Very stable with voltage and usually non-polarized

ESR: Low ESR and low dissipation factor

Applications: Audio circuits, Precision filters, Snubbers, AC coupling, DC link and pulse circuits.

Electrolytic Capacitors

Stability: Moderate; strongly affected by temperature and lifetime rating

Voltage behavior: Polarized; must be used within rated voltage and polarity

ESR: Moderate to high ESR, lower for low-ESR families

Applications: Bulk power filtering, Input capacitors, Output capacitors, Energy storage, Audio coupling.

Tantalum Capacitors

Stability: Good compared with aluminum electrolytic capacitors

Voltage behavior: Polarized; requires voltage derating for reliability

ESR: Moderate ESR, low-ESR polymer variants available

Applications: Power rail bulk decoupling, Portable electronics, Timing hold-up, Space-limited designs.

Silver Mica Capacitors

Stability: Excellent stability over temperature

Voltage behavior: Very stable with voltage

ESR: Very low loss

Applications: RF tuned circuits, Oscillators, High-Q filters, Precision high-frequency networks.

Practical Dielectric Comparison

The table below is generated from the shared capacitor dielectric dataset. It is a practical design comparison, not a replacement for a manufacturer datasheet.

Practical comparison of common capacitor dielectric types
Dielectric	Stability	ESR / losses	Voltage behavior	Aging	Typical applications	Main caution
C0G / NP0	Very high stability, about 0 ±30 ppm/°C	Very low ESR at high frequency	Very low capacitance change with DC bias	Negligible aging	RF networks, Oscillators, Filters, Timing circuits, Precision analog circuits	Limited capacitance range, Higher cost per uF, Larger size for high values
X7R	±15% from -55°C to 125°C	Low ESR, suitable for decoupling	Capacitance can decrease significantly with DC bias	Ages logarithmically over time after last heat cycle	Power rail decoupling, Bypass capacitors, General filtering, Bulk ceramic capacitance	DC bias derating, Aging, Microphonic behavior in some applications
X5R	±15% from -55°C to 85°C	Low ESR	Strong capacitance reduction with DC bias, especially in small packages	Ages logarithmically over time after last heat cycle	Portable electronics, Digital decoupling, Low-voltage power rails, Compact filters	Limited upper temperature range, DC bias derating, Aging
Y5V	+22% / -82% from -30°C to 85°C	Low ESR, but capacitance stability is poor	Very large capacitance loss with DC bias	High aging compared with stable dielectrics	Noncritical bypassing, Low-cost consumer circuits, Loose filtering requirements	Poor tolerance, Poor temperature stability, Severe DC bias loss, High aging
Z5U	+22% / -56% from 10°C to 85°C	Low ESR for ceramic construction	Large capacitance change with DC bias	High aging compared with C0G and film capacitors	Noncritical decoupling, Consumer bypass capacitors, Loose-tolerance filtering	Poor stability, Limited temperature range, DC bias derating, Not suitable for precision circuits
Film	Good to excellent depending on film material	Low ESR and low dissipation factor	Very stable with voltage and usually non-polarized	Excellent long-term stability	Audio circuits, Precision filters, Snubbers, AC coupling, DC link and pulse circuits	Physically larger, Lower capacitance density, Higher cost for large values
Electrolytic	Moderate; strongly affected by temperature and lifetime rating	Moderate to high ESR, lower for low-ESR families	Polarized; must be used within rated voltage and polarity	Electrolyte dries over time; lifetime depends on temperature and ripple current	Bulk power filtering, Input capacitors, Output capacitors, Energy storage, Audio coupling	Polarized, Limited lifetime, Higher ESR, Large size, Leakage current
Tantalum	Good compared with aluminum electrolytic capacitors	Moderate ESR, low-ESR polymer variants available	Polarized; requires voltage derating for reliability	Good long-term stability when properly derated	Power rail bulk decoupling, Portable electronics, Timing hold-up, Space-limited designs	Polarized, Surge sensitivity, Derating required, Failure mode concerns
Silver Mica	Excellent stability over temperature	Very low loss	Very stable with voltage	Excellent aging behavior	RF tuned circuits, Oscillators, High-Q filters, Precision high-frequency networks	Limited capacitance range, Higher cost, Larger than comparable ceramics

How to Choose a Dielectric

Dielectric selection guidance by application
Design need	Preferred dielectric	Reason
Precision timing	C0G / NP0 or film	Low drift, low aging, and predictable capacitance.
Analog filters	C0G / NP0 or film	Stable value and low dielectric absorption improve accuracy.
Power decoupling	X7R or X5R	Low ESR and compact MLCC packages are useful near IC power pins.
Bulk energy storage	Electrolytic, polymer, or tantalum	High capacitance is available in practical sizes.
Audio coupling	Film or suitable electrolytic	Film is stable and non-polarized; electrolytic helps with large values.
RF circuits	C0G / NP0 or silver mica	Low loss and stable high-frequency behavior.
High-voltage pulse circuits	Film	Good pulse handling and stable voltage behavior.
Compact consumer electronics	X5R or X7R	High capacitance density with manageable tradeoffs.

Worked Examples

100 nF microcontroller decoupling

Design goal: Provide local charge near a digital IC power pin.

Preferred dielectric: X7R or X5R

Why: Low ESR ceramic capacitors work well for local bypassing, and compact MLCC packages are easy to place close to the IC.

Main caution: Check DC bias curves. A small-package 100 nF MLCC may lose capacitance at operating voltage.

Precision RC timing network

Design goal: Keep timing error low over temperature and operating life.

Preferred dielectric: C0G / NP0 or film

Why: Stable dielectrics reduce temperature drift, aging, dielectric absorption, and voltage-related capacitance change.

Main caution: C0G values are limited, while film parts may be physically larger than ceramic alternatives.

Buck converter output capacitor

Design goal: Support ripple current, transient load steps, and loop stability.

Preferred dielectric: X7R ceramic plus electrolytic or polymer bulk

Why: Ceramic capacitors provide low ESR at high frequency, while bulk capacitors add energy storage and damping.

Main caution: Account for DC bias, ripple current rating, ESR, temperature rise, and control-loop stability.

Audio coupling capacitor

Design goal: Pass low-frequency audio while minimizing distortion and leakage effects.

Preferred dielectric: Film or properly biased electrolytic

Why: Film capacitors are stable and non-polarized, while electrolytics provide large capacitance in smaller sizes.

Main caution: Electrolytic polarity, leakage, tolerance, and low-frequency impedance can affect performance.

High-voltage snubber capacitor

Design goal: Absorb switching energy and control voltage transients.

Preferred dielectric: Film

Why: Film capacitors handle pulse energy, AC stress, and voltage swing better than many high-K ceramics.

Main caution: Choose a part with suitable voltage rating, pulse current rating, and thermal margin.

RF matching network

Design goal: Maintain stable impedance and low loss at high frequency.

Preferred dielectric: C0G / NP0 or silver mica

Why: Both provide low dielectric loss and stable capacitance for high-Q RF circuits.

Main caution: Keep layout parasitics, package size, and self-resonant frequency in the design review.