TAP/TEP Technical Summary and
Application Guidelines
1.3.4 Temperature dependence of dissipation factor
Typical Curves-Dissipation Factor vs. Temperature
Dissipation factor varies with temperature as the typical
curves show to the right. For maximum limits please refer to
ratings tables.
10
100F/6V
1F/35V
5
0
125
80 100
-55 -40 -20
0
20 40 60
Temperature C
1.4 IMPEDANCE, (Z) AND EQUIVALENT SERIES RESISTANCE (ESR)
1.4.1 Impedance, Z
1.4.3 Frequency dependence of impedance and ESR
This is the ratio of voltage to current at a specified frequency.
Three factors contribute to the impedance of a tantalum
capacitor; the resistance of the semiconducting layer,
the capacitance, and the inductance of the electrodes and
leads.
ESR and impedance both increase with decreasing frequency.
At lower frequencies the values diverge as the extra contri-
butions to impedance (resistance of the semiconducting
layer, etc.) become more significant. Beyond 1 MHz (and
beyond the resonant point of the capacitor) impedance again
increases due to induction.
At high frequencies the inductance of the leads becomes a
limiting factor. The temperature and frequency behavior of
these three factors of impedance determine the behavior of
the impedance Z. The impedance is measured at 25°C and
100 kHz.
Frequency Dependence of Impedance and ESR
1.4.2 Equivalent series resistance, ESR
1k
Resistance losses occur in all practical forms of capacitors.
These are made up from several different mechanisms,
including resistance in components and contacts, viscous
forces within the dielectric, and defects producing bypass
current paths. To express the effect of these losses they are
considered as the ESR of the capacitor. The ESR is frequency
dependent. The ESR can be found by using the relationship:
100
10
1
0.1 μF
0.33 μF
1 μF
Tan ␦
2πfC
ESR =
10 μF
33 μF
where f is the frequency in Hz, and C is the capacitance in
farads. The ESR is measured at 25°C and 100 kHz.
0.1
0.01
100 μF
330 μF
ESR is one of the contributing factors to impedance, and at
high frequencies (100 kHz and above) is the dominant factor,
so that ESR and impedance become almost identical,
impedance being marginally higher.
100
100k
10k
1M
1k
Frequency f (Hz)
Impedance (Z)
ESR
152 ■ MAY 2013
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