Capacitor: General Specifications of the Capacitor Explained

Overview

The video explains key datasheet specifications and how they determine which capacitor type is suitable for a given electronic application (e.g., timing/wave shaping, decoupling, and filtering). It emphasizes that capacitor “real” behavior depends on test conditions and the operating environment.

Main capacitor specifications covered

Rated / nominal capacitance (C)

• The capacitance value the capacitor is designed for, shown on the capacitor and in the datasheet.
• Measured in farads; commercially it can range from picofarads up to hundreds of farads.
• Actual capacitance varies with:
  • Temperature
  • Frequency
  • Operating voltage
  • Age
• Datasheets specify test conditions (example given: an electrolytic capacitor rated 1 µF at 120 Hz and 0.25 V).

Tolerance

• The allowed deviation from the rated capacitance, expressed as a percentage (%).
• Varies by capacitor type (about 1% to 20% mentioned).
• Example: 20% tolerance means actual capacitance could be ±20% (e.g., 1 µF could be ~0.8–1.2 µF).
• Important when applications require tight capacitance accuracy.

Temperature range

• The operating temperature range over which the capacitor functions properly.
• Mentioned range: -55°C to 125°C (depends on type).

Temperature coefficient

• How capacitance changes with temperature, typically expressed as:
  • % over the full range, or sometimes
  • ppm/°C
• Example: ±1% means capacitance varies by ±1% across the operating temperature span.
• Also notes capacitance may depend on frequency and bias voltage.

Bias / frequency dependence (noted for ceramic, especially Class 2)

• For some capacitors—especially ceramic Class 2—capacitance can change significantly with applied bias voltage.
• This must be considered during selection.

Rated / nominal voltage

• The maximum DC (or peak pulse) voltage the capacitor can continuously withstand.
• Varies widely (about 10 V to 10 kV mentioned).
• Exceeding rated voltage can damage the capacitor, so the selection must ensure operating voltage stays below the rating.

Volumetric efficiency (size/space-oriented metric)

• Defined as capacitance per unit volume.
• Depends on the dielectric medium and dielectric thickness.
• Expressed as a C·V product per unit volume (where C = capacitance and V = rated voltage).
• Manufacturing improvements have improved volumetric efficiency over time.

Leakage current / insulation resistance

• The dielectric is not a perfect insulator, so leakage current flows.
• Leakage causes a voltage drop over time; datasheets specify the measurement time because leakage decreases and stabilizes after some period.
• Leakage current is commonly in the nA to µA range.
• For film/ceramic capacitors, leakage is often specified as insulation resistance (typically in gigaohms), defined as:

insulation resistance = applied capacitor voltage / leakage current

Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL)

ESR (series resistance)

• Capacitors behave non-ideally due to internal components:
  • ESR models AC losses (series resistance).
  • Parallel resistance corresponds to insulation/leakage behavior.
• Why ESR matters:
  • High AC currents cause power dissipation:
    • P = I²·ESR
  • This generates heat and increases temperature.
  • Reliability depends on keeping capacitor temperature within rated limits.
• Manufacturers may provide dissipation factor instead of ESR:
  • Dissipation factor relates ESR to the capacitor’s reactance at the test frequency.
• Goal: keep ESR / dissipation factor low to minimize heating.

ESL (series inductance)

• ESL is negligible at low frequency but becomes important at high frequencies.
• ESL causes a series resonant frequency:
  • Below resonance: capacitor behaves mainly capacitive
  • Above resonance: behaves more inductively
  • At resonance: impedance magnitude in the model is related to ESR
• For high-frequency applications, select capacitors with low ESL.

Conclusion / takeaway

Different capacitor types are chosen based on which datasheet specifications best match the application’s requirements—such as accuracy, voltage stress, temperature behavior, leakage, and AC/high-frequency performance.

The presenter previews that a next video will cover different capacitor types and their usage.

Main speaker/source

• Speaker: The presenter from the YouTube channel “ALL ABOUT ELECTRONICS”.