Dielectric Dissipation Factor

Formula

Description

The dissipation factor (DF), also called tan δ (loss tangent), quantifies the ratio of energy lost to energy stored per cycle in a capacitor. It equals ESR divided by the capacitive reactance: DF = ESR / Xc = ESR × ωC. A lower DF indicates a more ideal capacitor. C0G/NP0 ceramics have DF < 0.001 (0.1%), X7R ceramics have DF around 0.025 (2.5%), and aluminum electrolytics can exceed 0.1 (10%). DF is frequency-dependent and generally increases with frequency and temperature.

Variables

• DF — Dissipation factor, also tan δ (dimensionless)
• ESR — Equivalent series resistance (Ω)
• f — Measurement frequency (Hz)
• C — Capacitance (F)

Practical Notes

Quality factor Q = 1/DF. Capacitor datasheets specify DF at a standard test frequency (typically 120 Hz for electrolytics, 1 kHz or 1 MHz for ceramics). For resonant circuits and RF applications, use capacitors with the lowest possible DF. Film capacitors (polypropylene, polystyrene) offer very low DF, making them ideal for audio and RF applications.