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IEEE PSpice – Transient Analysis
1) Implement the schematic shown below. The input is a sinusoid with a DC offset of zero, an amplitude of 0.1
and a frequency of 1KHz.
2) Place voltage markers at the input and output.
Parts Used
Description
DC voltage source
Sinusoidal
voltage source
Resistor
741 op-amp
Run PSpice
School Version
Part Name
Library
Vdc
Source
Vsin
Source
Student Version
Part Name
Library
Vdc
Source
Vsin
Source
R
LM741
R
uA741
Analog
OP AMP
Analog
EVAL
Place Voltage and
Current Markers (or
Probes) ICONs
Voltage Marker
Performing a Transient Simulation
3)
4)
5)
6)
7)
8)
9)
10)
From the top toolbar select Pspice->New Simulation Profile
In the pop-up menu that appears type in a simulation name
Click on <CREATE>
You will see the pop-up menu below
Select Transient Analysis as an analysis type
Change the run time to 2msec
Click <OK> to close the window
To run the simulation from the top toolbar select: Pspice-> run OR the Run PSpice icon (see previous page)
Plotting
After the simulation is complete a new window will appear. Because we placed voltage markers at the inputs
and output of the circuit these two voltage traces are automatically plotted.
Plotting Additional Traces
To plot additional traces after a simulation has run.
11) In the window with the simulation results select: Traces-> Add Trace
12) The pop-up menu below will appear
On the left hand side are all the voltages and currents that are available to plot. On the right hand side are
mathematical functions that can be performed on these values.
The output variables are sensibly named: currents begin with an I, voltages with a V. For example I(R1) is
the current going through the resistor R1.
13) Select the current through resistor R1
14) Click <OK> - to close the window and plot the current
Deleting Traces
15) Click on the I(IR) icon at the bottom left of the simulation window
16) click <delete> to delete it
Cursors
After a simulation has run one can use cursors to get precise simulation values.
17) To activate the cursors click on the toggle cursor on icon at the top of the Simulation window (see below)
A small Probe Cursor window, shown below, will appear. Next to A1 are x and y values for the left
mouse cursor. Next to A2 are values for the right mouse cursor. dif shows the difference between the
values for the left and right mouse cursors
Toggle cursor on
18) Affiliate left cursor, A1, with the trace of V(VOUT) by clicking on its icon at the bottom of the simulation
window with the LEFT mouse button (see below)
19) Affiliate right cursor, A2, with the trace of V(VIN) by clicking on its icon with the RIGHT mouse button (see
below)
20) Click on the V(VOUT) trace with the LEFT mouse button to define the position of the A1 cursor. Crosshairs
will be shown corresponding X and Y values are displayed in the Probe Cursor window. The crosshairs can be
moved by dragging the mouse with the right button.
Note:
o The position of the A2 cursor is similarly controlled with the right mouse button
o The difference between the A1 and A2 cursors is shown in the Probe Cursor menu as well.
o Cursors A1 and A2 can be used for the same trace
Toggle curser icon
left mouse click here
Left mouse click
Right mouse click
AC simulation
Delete the voltage probe at the input and replace the Vsin part with either a Vac or Vsrc part from the Source
Library. It is possible to add a dc offset to this AC source here we have left it zero. Note that the parameter Vac
is one. This is the amplitude of the AC signal. Using an amplitude of one, causes the transfer function to
automatically be plotted.
R2
200K
Vsrc or Vac part from
SOURCE Library
Vcc-
V4
0Vdc
1Vac
TRAN =
Vcc+
4
uA741
2
-
V-
R1
Vin
OS1
10K
3
0
0
+
V+
OUT
OS2
1
+15Vdc
6
5
Vcc-
V1
V2
-15Vdc
Vout
V
0
0
U1
7
Vcc+
Performing an AC simulation
21)
22)
23)
24)
25)
26)
From the top toolbar in the schematic window menu select: PSpice ->Edit Simulation Profile
In the Simulation Settings window select AC Sweep/Noise as an analysis type
Enter the frequency range as shown below DO NOT START with 0, Note that 1M is equivalent to 1m = 10-3
Select Logarithmic instead of linear (This is more customary.)
Specify 10 points per decade
Click <OK> to close the window
Do NOT start
at ZERO!
27) To run the simulation from the top toolbar select: Pspice-> run OR click on the Run PSpice icon
28) When the simulation is complete you will see the following output.
You can see that the output at 1KHz appears to go to 20Volts even though the amplifier should saturate
at +15Volts.
20V
10V
0V
1.0Hz
V(VOUT)
10Hz
100Hz
1.0KHz
Frequency
10KHz
100KHz
1.0MHz
Creating Bode Plots
29) In the top toolbar of the simulation window select: Traces->Add Trace
There are a number of functions that are helpful for AC simulations. These, and others are shown on
the right panel of the Add Traces window. Below are some helpful functions:
Function
Function name
Phase
P()
Magnetude
M()
dB
dB()
Imaginary Part
IMG()
Real Part
R()
30) Plot the phase of the transfer function by plotting the function P(V(Vout)) as shown below.
31) Click <OK> to close the window and plot the phase
Below is a plot of the phase. Remember the gain for low frequencies is -20. This is represented with a180
degree phase shift.
173d
130d
87d
50d
1.0Hz
P(V(VOUT))
10Hz
100Hz
1.0KHz
10KHz
100KHz
1.0MHz
Frequency
Showing the magnitude as a separate plot (a strip chart)
32)
33)
34)
35)
From the top toolbar of the schematic window with the waveforms select: Plot-> Add Plot to Window.
From the top toolbar of the simulation window select: Traces->Add Trace
Plot the magnitude of the transfer function by plotting the function M(V(Vout))
Click <OK> to close the window and plot.
A transient simulation with a digital pulse and initial condition
36) Build the simple RC circuit shown below. Add voltage markers to the input and output.
37) The part IC1 is used to assign an assign the initial condition of 2Volts at the node Vout.
PART
LIBBARY
Resistor
R
ANALOG
Capacitor
C
ANALOG
digital waveform
Vpulse
SOURCE
Initial condition
IC1 or IC2 (IC1 shown)
SPECIAL
+ IC= 2V
R1
Vin
Vout
1k
V1 = 0
V2 = 5
TD = 1u
TR = 1n
TF = 1n
PW = 1u
PER = 2u
V1
V
V
C1
0.1n
0
Parameter
V1
V2
TD
TR/TF
PW
PER
Description
First Voltage
Second Voltage
Delay Time
Rise/Fall time
Pulse width
Period
There are two parts that are helpful for digital Spice simulations.
One is Vpwl and the other is Vpulse. Here we are using Vpulse the
parameters necessary for Vpulse are summarized below.
38) Run a Transient simulation simulating from 1-4usec
39) The output should appear as follows
5.0V
2.5V
0V
0s
V(VOUT)
0.5us
V(VIN)
1.0us
1.5us
2.0us
Time
2.5us
3.0us
3.5us
4.0us