IEEE PSpice – Transient Analysis
Below is an amplifier in a feedback system that is expected to have a closed loop gain of -20. The circuit has a
sinusoidal input with a DC offset of zero, an amplitude of 0.1 and a frequency of 1KHz.
Net Aliases
How to place a net alias: From the top menu: Place->Net alias OR from the side tool bar Place net alias ICON
To create a more readable and less cluttered schematic we have named nets used net aliases. (This also helps
with plotting) When nets have the same name they are considered to be connected. Here, for example, Vcc- on
the opamp is assumed to be connected to Vcc- the -15 V DC voltage supply. We have also named ground the
number zero.
Placing Voltage/Current Markers
How to place Voltage/Current Markers: From the top menu: Place->Marker->Voltage OR top toolbar ICON
Placing a Voltage or Current Marker causes the voltage or current indicated to automatically be plotted after a
simulation has run.
Run PSpice
Place Voltage and
Current Markers (or
Probes) ICONs
Place net
alias ICON
Vsin
Voltage Marker
Placing parts (see next page)
Placing parts
How to place parts: From the top menu: Place->Part OR hotkey p
After hitting hotkey p the pop-up menu shown below will appear. Here all libraries are selected (you can just
select a subset of libraries). In the “parts list” the part is listed along with the library that it belongs to. It is
important to add the part from the correct library. Otherwise it may not function as you intend. As you can see
below there are multiple parts that are called R, and each is in a different library.

To search through all libraries for your part. click on the menu where indicated and hit <ctrl> a

Enter the name of the part that you wish to add by scrolling or typing it directly.

Hit <OK> - this will close the menu

Sometimes you will see a pop-up menu indicated that the part is not in the design cache. If you see this
menu Hit <yes>.

Move your cursor to where you want to place the part on your schematic. Click your mouse at the location

You will continue to be able to place parts that are of the type that you selected. Hit <esc> to end the place
part command.
library
part
Click here and hit
<ctrl>a to select all
libraries
Description
DC voltage source
Sinusoidal
voltage source
Resistor
741 op-amp
School Version
Part Name
Library
Vdc
Source
Vsin
Source
Student Version
Part Name
Vdc
Vsin
Library
Source
Source
R
OP AMP
R
EVAL
Analog
uA741
Analog
LM741
Simulating







From the main menu select Pspice->New Simulation Profile
In the pop-up menu that appears type in a simulation name
Hit <CREATE>
You will see the pop-up menu below
Select Transient Analysis as an analysis type
Change the run time to 2msec
Hit <OK> This will close the window

To run the simulation from the main menu: Pspice-> run OR Run PSpice from the top toolbar
Plotting
After the simulation is complete a new window will appear. Because we placed voltage markers at the inputs and
outputs these two voltages are automatically plotted. Sometimes the markers do not work or in debugging a circuit
one wants to examine other voltages or currents.
4.0V
2.0V
0V
-2.0V
0s
V(VOUT)
0.2ms
V(VIN)
0.4ms
0.6ms
0.8ms
1.0ms
Time
1.2ms
1.4ms
1.6ms
1.8ms
2.0ms
Adding Traces
To plot traces after a simulation has run. In the window with the simulation results go to: Traces-> Add Trace
 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 the output variables
 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 called R1. – This is why it is helpful to name nets
 With your mouse select the Voltage or current that you wish to plot
 Hit <OK> - the windoiw will close at he plot should apprear
Cursers
After a simulation has run one can use cursers to get exact data values from simulation. There are two cursers one
affiliated with the left mouse button and the other with the right mouse button
 In the window with your simulation traces plotted hit the Toggle Curser ICON on the top toolbar
 With your left mouse button click on the trace that you wish to plot at the bottom. Here we have
selected V(VOUT)
 With your left mouse button select the position on the trace that you want a value for. A crosshair
curser will appear and its value displayed in the Probe Curser window as A1
 The process can be repeated with the right mouse button to create a second curser.
Toggle curser ICON
Then left mouse click
here
Left mouse click here
Including Simulation Plots in Reports
The Plotted simulation results can easily be copied to the clipboard and then pasted using <ctrl> V in a Microsoft
Word Document.
To copy to the clipboard: From the main menu: Window->Copy To Clipboard
Resimulation
 At this time close the window where you simulation is plotted and return to the window with your schematic.
 Modify the parameters of your Vsin part so that the magnitude of the amplitude is 1 Volt.
V3

VOFF = 0
VAMPL = 1
FREQ = 1K
Resimulate. Note the clipping; the maximum output voltage should be +20Volts, but the
amplifier saturates. In our next simulation we shall see that his goes away.
20V
saturation
0V
-20V
0s
V(VOUT)
0.2ms
V(VIN)
0.4ms
0.6ms
0.8ms
1.0ms
Time
1.2ms
1.4ms
1.6ms
1.8ms
2.0ms
AC simulation
Replace the Vsin part with either the Vac or Vsrc part from the Source Library. It is possible to ad a dc offset to this
AC source here we have left it zero. Note that the parameter Vac is one. This is the magnitude of the AC signal.
99.9% of the time this is a very good choice. This causes the transfer function to automatically be plotted. With this
type of simulation, spice is unable to tell that the amplifier will saturate.
R2
Vsrc or Vac
part from
SOURCE
Library
200K
Vcc-
V4
0Vdc
1Vac
TRAN =
Vcc+
4
uA741
2
-
V-
R1
Vin
OS1
10K
3
0
0
+
V+
OUT
OS2
+15Vdc
6
5
Vcc-
V1
1
V2
-15Vdc
Vout
V
0
0
U1
7
Vcc+
Performing the AC simulation
 From the schematic window menu: PSpice ->Edit Simulation Profile
 Select AC Sweep/Noise
 Enter the frequency range DO NOT START with 0, Note that 1M is equivalent to 1m = 10 -3
 Logarithmic is customary
 Hit <OK> to close the window
Do NOT start
at ZERO!
To run the simulation In the Schematic window menu: PSpice->Run
Below is the output. You can see that the output at 1KHz appears to go to 20Volts even though the amplifier should
saturate at +15Volts. Since the magnitude of Vin is one by plotting Vout we have in effect plotted Vout/Vin, the
transfer function of the circuit.

To remove a trace select it at the bottom and then hit <delete>
20V
10V
0V
1.0Hz
V(VOUT)
10Hz
100Hz
1.0KHz
10KHz
100KHz
1.0MHz
Select: then hit <delete> to Frequency
remove
Plotting traces from an AC simulation:
 When the simulation has complete in the window containing the plotted output variables. From the main menu
of this window : Traces->Add Trace
 There are a number of functions that are helpful for AC simulations. Below we are plotting the phase. Again
here it is helpful that we have named the output Vout.
Function
Phase
Magnetude
dB
Imaginary Part
Real Part
Function name
P()
M()
dB()
IMG()
R()
Below is a plot of the phase. Remember the gain for low frequencies is -20. This is represented with the 180 degree
phase shift.
173d
130d
87d
50d
1.0Hz
P(V(VOUT))
10Hz
100Hz
1.0KHz
10KHz
100KHz
Frequency
New Simulation:
Replace the 200K resistor with a 5nF capacitor (C from the ANALOG Library).
C2
5n
VccVin
V4
0Vdc
1Vac
TRAN =
Vcc+
4
uA741
2
-
V-
R1
OS1
10K
0
0
+
V+
OUT
3
OS2
V1
1
+15Vdc
6
5
VccV2
-15Vdc
Vout
V
0
0
U1
7
Vcc+
Perform an AC simulation from 1 to 1MHz plotting dB and phase.
1.0MHz
Another Transient Simulation: Step response of an RC filter
Build the simple RC circuit shown below with the parts and markers indicated. Now capacitors can have initial
conditions. Here we use the part IC1 to assign the initial condition of 2Volts at the node Vout.
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.
+ IC= 2V
R1
Vin
Vout
1k
V1
V1 = 0
V2 = 5
TD = 1u
TR = 1n
TF = 1n
PW = 1u
PER = 2u
V
V
C1
0.1n
0
Resistor
Capacitors
Vpulse
(digital
waveform)
Initial
condition
Parameter
V1
V2
TD
TR/TF
PW
PER
PART
R
C
Vpulse
LIBBARY
ANALOG
ANALOG
SOURCE
IC1 or IC2
(IC1 shown)
SPECIAL
Description
First Voltage
Second Voltage
Delay Time
Rise/Fall time
Pulse width
Period
I.C. of 2 volts
Run a Transient simulation simulating from 1-4usec
He 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