The Capacitor
Impedance vs. Frequency
Effect of Capacitance – AVX SpinGuards
10.00
Log Impedance, Ohms
+1.5
0
1.00
.001mF
.01mF
0.10
.1mF
.33mF
0.01
1
10
100
Log Frequency, MHz
1000
Capacitance Change Percent
-1.5
Typical Curve of Aging Rate
X7R Dielectric
-3.0
-4.5
-6.0
-7.5
Impedance vs. Frequency
Effect of Dielectric – AVX DIPGuards
10.0
(NP
G F
C0 01
.0
1
10
100
1000 10,000 100,000
Hours
Figure 9
Characteristic
C0G (NP0)
X7R
Z5U
Y5V
Max. Aging Rate %/Decade
None
2
3
5
X7
R
1
.0
0)
Log Impedance, Ohms
R
X7
R
X7
F
F
22
F
.0
F
F
47
.0
.22
0.1
R
Z5U
X7
1.0
Effects of Mechanical Stress –
High “K” dielectric ceramic
capacitors exhibit some low level piezoelectric reactions
under mechanical stress. As a general statement, the
piezoelectric output is higher, the higher the dielectric con-
stant of the ceramic. It is desirable to investigate this effect
before using high “K” dielectrics as coupling capacitors in
extremely low level applications.
100
200
0.1
1
10
Log Frequency, MHz
Reliability –
Historically ceramic capacitors have been one
of the most reliable types of capacitors in use today.
The approximate formula for the reliability of a ceramic
capacitor is:
L
o
=
L
t
V
t
V
o
X
Impedance vs. Frequency
Effect of Lead Length – Military CKR05 .01mF
100.0
Log Impedance, Ohms
.500"
.250"
.062"
0"
T
t
T
o
Y
where
L
o
= operating life
T
t
= test temperature and
L
t
= test life
T
o
= operating temperature in °C
V
t
= test voltage
V
o
= operating voltage
X,Y
= see text
10.0
1.0
0.1
1
10
100
Log Frequency, MHz
1000
Historically for ceramic capacitors exponent X has been
considered as 3. The exponent Y for temperature effects
typically tends to run about 8.
Figure 8
7
AVX [ AVX CORPORATION ]
