Impedance
Parameters
All circuit components, resistors, capacitors or inductors, have
parasitic comp onents lurking in the shadows waiting for the unwary,
for example unwanted resistance in capacitors, unwanted capacitance
in inductors, and unwanted inductance in resistors. Thus simple
components should b e mo deled as complex imp edances, for in fact
that is what they are!
Figure 6-1 (A) shows the imp edance denitions and (B) shows vector
representation of imp edance. Impedance,
Z
is the total opposition
that a circuit or device oers to the ow of alternating currentata
given frequency.
Z
contains a real and an imaginary part, and it is
expressed in rectangular form as Resistance and Reactance, or in
polar form as magnitude of Impedance and Phase as follows.
Z = R + jX =
j
Z
j
6
j
Z
j
=
p
R
2
+X
2
= arctan
j
X
j
R
R=R
s
Where,
Z: Imp edance [ ]
R: Resistance [ ]
X: Reactance [ ]
j
Z
j
: Magnitude of Impedance [ ]
: Phase of Impedance [deg or rad]
R
s
: Series Resistance [ ]
6-2 Measurement Procedure and Examples
To Next Page
