
KEMET Electronics Corporation, P.O. Box 5928, Greenville, SC 29606 (864) 963-6300
Performance Characteristics
4. Capacitors show no visible mechanical damage
or leakage of electrolyte.
11. Reverse Voltage
When subjected to a DC potential of 3 volts,
applied in the reverse polarity direction for 125 hours ±
10 hours, capacitors shall meet the following require-
ments.
- DC Leakage: shall not exceed 1.25 times initial
limit
- Capacitance: shall be within stated tolerance
(K- ±10%, M- ±20%, J- ±5%)
- Dissipation Factor: shall not exceed initial limit
12. Equivalent Series Resistance (ESR)
Equivalent Series Resistance (ESR) is the pre-
ferred high-frequency statement of the resistance
unavoidably appearing in these capacitors. ESR
decreases with increasing frequency. Typical ESR lim-
its are established in each specific product series.
However, the ESR limits provided are for reference
only, and are not necessarily the actual value that a
particular Series product will attain.
Total impedance of the capacitor is the vector sum
of capacitive reactance (X
c
) and ESR, below reso-
nance; above resonance total impedance is the vector
sum of inductive reactance (X
L
) and ESR. See Figure 4.
To understand the many elements of a capacitor, see
Figure 5.
Figure 5. The Real Capacitor
A capacitor is a complex impedance consisting of
many series and parallel elements, each adding to the
complexity of the measurement system.
ESL
– Represents lead wire and construction
inductance. In most instances (especially in
tantalum and monolithic ceramic capacitors) it is
insignificant at the basic measurement frequen-
cies of 120 and 1000 Hz.
ESR
– Represents the actual ohmic series resist-
ance in series with the capacitance. Lead wires
and capacitor electrodes are contributing sources.
RL
– Capacitor Leakage Resistance. Typically it
can reach 50,000 megohms in a tantalum capaci-
tor. It can exceed 10
12
ohms in monolithic ceram-
ics and in film capacitors.
Rd
– The dielectric loss contributed by dielectric
absorption and molecular polarization. It becomes
very significant in high frequency measurements
and applications. Its value varies with frequency.
Cd
– The inherent dielectric absorption of the
solid tantalum capacitor which typically equates to
1-2% of the applied voltage.
As frequency increases, X
c
continues to decrease
according to its equation above. There is unavoidable
inductance as well as resistance in all capacitors, and
at some point in frequency, the reactance ceases to be
capacitive and becomes inductive. This frequency is
called the self-resonant point. In wet tantalum capaci-
tors, the resonance is damped by the ESR, and a
smooth, rather than abrupt, transition from capacitive to
inductive reactance (XL = 2
π
fL) follows.
Despite the fact that the reactance is nearly all
inductive above the self-resonance, these capacitors
find use as decoupling devices up to 10MHz.
ESR and Z are also affected by temperature. At
100 kHz, ESR decreases with increasing temperature.
The amount of change is influenced by the size of the
capacitance and is generally more pronounced on
smaller ratings.
5
2
π
fC
1ohm
Xc=
where:
f = frequency, Hertz
C = capacitance, Farad
Figure 4a: Total Impedance of the Capacitor Below Resonance
X
L
= 2
π
fL
where:
f = frequency, Hertz
C = capacitance, Farad
Figure 4b: Total Impedance of the Capacitor Above Resonance