PSpice Basic Examples
Hayder Radha - ECE202
Example Capacitor (Tran.)
* Lines with the star symbol (*) are used for comments
* SIN (<DC offset><amplitude><frequency><timedelay><damping factor> <phase >)
VS 1 0 SIN (0
100
200
0
0
90)
C1 1 0 0.5U
.PROBE
* .TRAN <print step value> <final time value>+[no-print value [step ceiling value]]
.TRAN
100U
20M
0
100U
.END
The above PSpice program performs analysis in the timedomain using the ".TRAN" mode/command.
The program specifies a sinusoidal source (SIN) with:
<amplitude> = 100 V that operates at a particular:
<frequency> = f = 200 Hz.
Note that a <phase> = 90 degree is specified within the
SIN function. This provides a "cosine" source. In general,
if the desired phase of the "cosine" source is ( φ ), then the
"phase" parameter should be set to: ( φ + 90).
Note that in this example:
The time-period associated with a complete
cycle = T = 1/f = 5 milliseconds. We need to
keep this value in mind when specifying the
parameters of the ".TRAN" command.
For example, the <print step value> parameter
specifies the step-size (in units of time) that
PSpice would use to analyze and plot the
different signals of the circuit. In general, this
parameter should be much smaller than T.
Here, we selected a <print step value> = 100
microseconds (100U).
The <final time value> parameter specifies the
end-time for the desired analysis/plots. Here
and again, we need to take the value T=5msec
into consideration. You need to analyze and
plot the circuit over multiple cycles. Here we
selected <final time value> = 20 milliseconds
(20M). This represents four (20/5) cycles of
the desired signals (at frequency f = 200Hz).
Example Capacitor
Date/Time run: 09/12/04
Temperature: 27.0
(A) ex_capacitor (active)
100V
0V
-100V
V(1)
100mA
0A
SEL>>
-100mA
I(C1)
1
100mA
0A
-100mA
2
100V
0V
>>
-100V
0s
1
5ms
I(C1)
2
10ms
15ms
20ms
V(1)
Time
Date: September 12, 2004
Page 1
Time: 23:34:40
From the above plots for the current and
voltage across the capacitor, we clearly see a
"shift" between the two signals. We can use
PSpice to measure this "shift" in time:
ts = 1.25 milliseconds.
This translates into a phase (angle) shift of φ
that we can evaluate using the relationship
between ts and φ :
ts =φ/ω.
Note that a phase shift of 90 degree is what we
expect between the current and voltage signals across
a capacitor.
Also note that the current signal "leads" the voltage
signal. For example, the peak value of the current
signal happens "earlier" than the corresponding peak
value of the voltage signal.
AC Analysis with PSpice
It should be clear that measuring the phase angle
by using the above PSpise program is rather
cumbersome.
Another approach is to use "AC" analysis under
PSpise. In this case, we can analyze the circuit
over any desired range of frequencies. We can
also easily measure the magnitude and phase of
any desired signal in steady-state at any desired
frequency.
The following example illustrates a PSpice AC
analysis of the same (above) simple circuit.
Example Capacitor (AC)
*
VS 1 0
AC <magnitude> <phase>
AC
100
0
C1 1 0 0.5U
.PROBE
*.AC <sweep><points><start freq><end freq>
.AC LIN 100
.END
1Hz
200Hz
VM(1) / IM(C1)
IM(C1)
VM(1)
Date/Time run: 09/13/04
200V
100V
0V
100mA
50mA
0A
400K
200K
SEL>>
0
0Hz
Date: September 13, 2004
50Hz
Example Capacitor (AC)
(A) ex_capacitor_AC (active)
100Hz
Frequency
Page 1
150Hz
Temperature: 27.0
200Hz
Time: 00:18:10
We used PSpice to plot the ratio of the voltage magnitude
(VM) to the ratio of the current magnitude (IM) across the
capacitor. This ratio represents the magnitude of the
impedance (|V|/|I|=|Z|) of the capacitor. As expected, the
capacitor's impedance decreases as we increase the
frequency.
From the above plot for the capacitor's impedance
magnitude (VM/IM), it is difficult to observe the actual
impedance values over a wide range of frequencies. Below,
we modify the frequency range for our PSpice analysis in
order to gain a better insight into the capacitor's impedance
over that range.
Example Capacitor (AC)
*
VS 1 0
AC <magnitude> <phase>
AC
100
0
C1 1 0 0.5U
.PROBE
*.AC <sweep><points><start freq><end freq>
.AC LIN 100
.END
100Hz
200Hz
IM(C1)
VM(1)
Date/Time run: 09/13/04
200V
100V
SEL>>
0V
75mA
50mA
25mA
3.5K
3.0K
2.5K
2.0K
1.5K
100Hz
VM(1) / IM(C1)
Date: September 13, 2004
120Hz
Example Capacitor (AC)
160Hz
(A) ex_capacitor_AC (active)
140Hz
Frequency
Page 1
180Hz
Temperature: 27.0
200Hz
Time: 00:00:51
The AC analysis under PSpice could be used to
evaluate the phase of any desired signal. Also, we can
plot two or more functions in the same figure. In the
plots shown below, we used PSpice to plot the
magnitude and the phase of the different signals.
Note that the phase for the capacitor's current is 90
degree over all frequencies. This is the case for this
simple (capacitor-only) circuit. For more complex
circuits the phase could change over frequency.
We also plotted the difference between the voltage
phase (VP) and the current phase (IP). This phase
difference (VP-IP) represents the phase of the
capacitor's impedance. Note that the resulting phase of
the capacitor's impedance is negative 90 degree over all
frequencies. This is consistent with our expectation.
Recall the "−j" factor in the capacitor impedance:
Z = −j ( 1/ω C ) = | 1/ω C | ej(-90) . Hence, and as we
expect, the capacitor's impedance phase (-90 degree) is
constant over all frequencies whereas the magnitude is
a function of the frequency.
Therefore, we can use PSpice to evaluate the impedance
of any device by observing its impedance's magnitude
and phase over any desired range of frequencies.
1.0ud
0d
-1.0ud
2
2
150V
100V
50V
>>
0V
100mA
50mA
180d
90d
0d
0A
2
>>
0d
400K
-100d
1
IP(C1)
VP(1)
2
2
VM(1)
Example Capacitor (AC)
Frequency
100Hz
(A) ex_capacitor_AC (active)
Page 1
50Hz
2
VP(1)- IP(C1)
IM(C1)
VM(1) / IM(C1)
1
Date/Time run: 09/13/04
1
1
1
200K
0
SEL>>
>>
-200d
0Hz
1
Date: September 13, 2004
150Hz
Temperature: 27.0
200Hz
Time: 00:40:34