Specifications

1.9 Reactance chart
The reactance chart shows the impedance and admittance values of pure capacitance or inductance
at arbitrary frequencies. Impedance values at desired frequencies can be indicated on the chart
without need of calculating 1/(wC) or wL values when discussing an equivalent circuit model for a
component and also when estimating the influence of parasitics. To cite an example, impedance
(reactance) of a 1 nF capacitor, which is shown with an oblique bold line in Figure 1-20, exhibits
160 kΩ at 1 kHz and 16 Ω at 10 MHz. Though a parasitic series resistance of 0.1 Ω can be ignored at
1 kHz, it yields a dissipation factor of 0.0063 (ratio of 0.1 Ω to 16 Ω) at 10 MHz. Likewise, though a
parasitic inductance of 10 nH can be ignored at 1 kHz, its reactive impedance goes up to 0.63 Ω at
10 MHz and increases measured capacitance by +4 percent (this increment is calculated as 1/(1 –
X
L
/X
C
) = 1/(1 – 0.63/16).) At the intersection of 1 nF line (bold line) and the 10 nH line at 50.3 MHz,
the parasitic inductance has the same magnitude (but opposing vector) of reactive impedance as
that of primary capacitance and causes a resonance (SRF). As for an inductor, the influence of para-
sitics can be estimated in the same way by reading impedance (reactance) of the inductor and that
of a parasitic capacitance or a resistance from the chart.
Figure 1-20. Reactance chart
Frequency (Hz)
1
0
n
H
1
0
0
p
H
1
n
H
1
0
p
H
1
p
H
1
0
0
n
H
1
µ
H
1
0
µ
H
1
0
0
µ
H
1
m
H
1
0
m
H
1
0
0
m
H
1
H
1
0
H
1
0
0
H
1
k
H
1
0
k
H
1
0
a
F
1
0
0
a
F
100 p
F
1
n
F
1
0
p
F
1
p
F
1
0
n
F
100 n
F
1
µ
F
1
0
µ
F
1
0
0
µ
F
1
m
F
1
0
m
F
1
0
0
m
F
1
0
f
F
100 fF
1
f
F
100
1 k 10 k 100 k 1 M 10 M 100 M 1
G
C
L
10
0
1 k
10
k
100
k
1
M
10
M
100
M
10
1
100 m
10 m
1
m
|Z|
1-15