OrCAD PSpice 9.2
We will use Orcad schematic capture
program and PSPice to simulate the circuits.
- Start the Orcad schematic capture
program (Start -> Programs -> Orcad Family Release 9.2 Lite Edition ->
Capture Lite Edition)
- Start a new project (or open an
existing one) (File -> New -> Project...)
- In the dialog that opens,
provide a project name, a file path to where you want your project stored,
and select the item "Analog or Mixed-Circuit Wizard". Click OK.
Placing parts, editing parts, and
wiring the circuit
- Create the schematic by
picking a DC voltage source. Select "Part" from the "Place" menu (or click
on the second item in the vertical toolbar) to open a dialog that allows you
to choose the part you want to use. For first time user, you need to add
library by clicking on Add Library. After that, you need to choose the
library from the lower list and then pick the particular library part from
the upper list. From the library list, choose SOURCE and then from parts
list choose VDC. You should see a DC voltage source symbol appear in the
pane at the bottom. Click OK.
- Placing the voltage source
You will be returned to the
drawing window. The symbol of a DC voltage source will be attached to the
cursor. Drag it to point in drawing window and click the left mouse to place
it. A voltage source symbol will remain attached to the cursor (in case you
wanted to place more voltage sources). To get rid of it, click the right
mouse button and choose "End mode" from the pop up menu. If you don't like
where you've located the source, you can select it and move it to a new
- Place other components
Now add transistor and other
parts using the same method to pick and place the parts. Transistor are in
the Breakout library. Note that there are a number of transistor choices in
the library. Choose the correct one for this design.
- Wire the parts together and
add the ground connection
Use the wire tool to connect the
parts. Select the "Wire" item from the "Place" menu (or click on the third
item in the vertical toolbar) to activate the wire tool. To wire the nodes
together, click on an end of one part, drag the mouse to the end of another
part and click again.
Every SPICE circuit needs a
ground connection. To add a ground, use the menu (Place -> ground). A dialog
opens. Choose the symbol 0 from the library
Place the ground in the desired place and then use the wire tool to connect
it into the circuit.
- Device model
Some devices (semiconductor devices
in particular) that are included in SPICE require many parameter values.
Often, many devices in a circuit are defined by the same set of device model
parameters. For these reasons, a set of device model parameters is defined
on a separate .MODEL line and assigned a unique model name in the PSpice
Model Editor Lite.
To set the parameter of the device,
select the device and go to Edit->Pspice model. Click it to open PSpice
Model Editor Lite.
Copy the parameter from
SPICE Model Link. Save the file before you close the program.
- Changing parameters
When the components were placed,
the names and values were set to defaults. Generally, we need to use other
component values and would like the option of picking our own names. The
schematic capture program provides two methods for changing the properties
of components. The name or value can be changed by double-clicking directly
on either the name or the value and typing in the new value in the dialog
that appears. Note that you can also move the name and value labels around
on the schematic in order to make things easier to read.
The other way to change names and
parameters is to double-click on the part symbol directly (or select it with
a single click and choose "Properties..." from the "Edit" menu or click once
to select it and then right-click to bring up a pop-up menu from which you
can choose "Edit Properties...".) A dialog will appear that has all of the
properties (names and parameters) for the part. These can be edited in the
dialog. Don not forget to set transistors' length and width.
- Setting up the analysis
Now that the circuit is
completed, you are ready to tell PSPICE how to analyze the circuit. From the
"PSPICE" menu, select the menu item "New Simulation Profile". A small dialog
appears that asks you to give a name to the simulation profile you are
creating. Choose something like "Transient Analysis" and click on "Create".
Another dialog with many tabs appears. The only tab that is important at
this point is the one labeled "Analysis". In this case, we want to do a
transient analysis of the circuit, so we want to choose "Time Domain
(Transient)" in the pop-up menu. In an Transient analysis, PSPICE will run
certain time as user specified. For this example, set the Running Time to
20ns and Start time to 0. When finished entering all the information for the
Transient Analysis, click OK (or Apply)
- Running the analysis
Now that everything is set up in
the Capture program, we turn the analysis over to PSPICE. Start the
simulation by choosing "Run" from the "PSPICE" menu or by clicking on the
"run triangle", which is the third item in the second horizontal toolbar.
After a few seconds (if there are no errors) the analysis will finish and
SPICE will automatically launch Probe. You should see a window with an empty
plot in it. Since we did an Transient analysis, the x-axis on the plot will
be the time. If there are errors, you can get some clue to the nature of the
problem by examining the text in the lower left box in the window.
- Plotting the data
All that's left is to make the
plot showing the calculated results. To make the plot, we must add a trace.
From the "Trace" menu, choose the item "Add Trace..." (or click on the Add
Trace item in the second toolbar
and a dialog will appear. On the left side of the dialog is a list all of
the circuit variables that can be plotted. (It may take some trial and error
to determine what each of the variables represent.) On the right is a list
of mathematical functions that can be utilized in making the plot. On the
left, click on "V1(V2)" and "V(Vout)", which is the voltage of the pulse
source and "Vout" output port. Click OK when ready. You should see a plot
like the one below.
If you see the above curve, all has
been done for this assignment.
This webpage is adapted from "http://tuttle.merc.iastate.edu/ee333/spice/pspicetutorial/basics/pspicebasics.htm"