4.2 Impedance and Admittance
171
For the series R-L network of Figure 4.2-21 the calculation is identical.
The Q which we have defined for series and parallel R-C and R-L networks is also a very
useful parameter to work out series to parallel and parallel to series conversions. These conversions
can be very useful when it comes to circuit analysis since they allow us to simplify it considerably. Let
us now go through an example.
Figure 4.2-34 Series R-C network in MWO
Consider the R-C network shown in Figure 4.2-34. The impedance of the R-C network is
The
Q of this network is therefore
Now we can use specific formulae, the derivation of which is beyond the scope of this treatment, to
convert our R-C series network to an R-C parallel equivalent.
To this end we first calculate our equivalent parallel resistor value
, which is derived from the
value of our series resistor
and the Q of the series circuit . This is shown below
( )
Then
we calculate the value of our equivalent parallel capacitor
, by using and ,
as shown below
(
)
The parallel R-C equivalent is shown in Figure 4.2-35.
Figure 4.2-35 Parallel R-C network equivalent to the series R-C shown in Figure 4.2-34
ACVS
ID=V1
Mag=1 V
Ang=0 Deg
Offset=0 V
DCVal=0 V
CAP
ID=C1
C=7.95 pF
RES
ID=R1
R=10 Ohm
ACVS
ID=V1
Mag=1 V
Ang=0 Deg
Offset=0 V
DCVal=0 V
CAP
ID=C1
C=6.36 pF
RES
ID=R1
R=50 Ohm
Conquer Radio Frequency
171 www.cadence.com/go/awr
