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DC Sweep Tutorial (325)
First Create the schematic shown below (see create schematic tutorial)
Parts used for schematic
Part Name
Vsrc
Q2N2222
R
CPP Library
Source
Bipolar
Analog
Description
Voltage source
BJT
resistor
Placing Probes
To automatically plot results when a simulation is complete place voltage probes to plot voltages or
current probes for currents.
1) Place a voltage probe and current probe as shown below. Note current probes must be placed on the pins
of devices (the very end)
Current probe
Voltage probe
Running a DC sweep
2) To simulate from the top toolbar select Pspice->New Simulation Profile
3) Enter a name
4) Click on create to close the window
5) In the Simulation Settings menu (shown below) select a DC sweep analysis type
6) Specify that you wish to sweep a voltage source
7) Specify the voltage source that you wish to sweep (V1)
8) Specify the Start and stop voltages as well as the voltage increment
Note: Spice understands m to be 10-3
9) Click on <OK> to close the window
10) To simulate click on the run Pspice icon at the top of the schematic
Run Pspice
icon
11) The simulation will run
Note if your simulation fails check for errors: from top toolbar: Window->Session Log
12) If your simulation runs successfully the voltage and current will be plotted as shown below (the current is so
small in comparison to the voltage it will appear to be zero) (see below)
Deleting Traces
13) Click on the V(Vo) icon at the bottom left of the simulation window (as shown below)
14) click <delete> to delete it
15) Also delete the current trace
V(Vo) ICON
Plotting Expressions
In this example you will plot Ic/Ie as well as Vb
16) In the top toolbar of the Allegro Simulation Simulator window select: Trace->Add Trace
You will see the Add Traces pop-up menu shown below. On the left circuit voltages and currents are listed on
the right available functions
17) Enter the expressions as indicated
18) Select <OK> to close the window and plot the expressions
Using Cursors
Cursors can be used to determine precise simulation values.
19) To activate the cursors click on the toggle cursor on icon at the top of the Simulation window
Toggle cursor on
There are two cursors A1 and A2. A1 is controlled with the left mouse and A2 with the right.
20) Affiliate cursor A1 with the trace of Ic/Ie by clicking on its icon with the LEFT mouse button (see below)
21) Affiliate cursor A2 with the trace of Vb by clicking on its icon with the RIGHT mouse button (see below)
22) Click on the actual Vb trace with the RIGHT mouse button to define the position of the A2 cursor. Crosshairs
will be shown. X and Y values for this trace at the position of the cross hairs are displayed in the small Probe
Cursor window. The crosshairs can be moved by dragging the mouse with the right button.
Note:
o The position of the A1 cursor is similarly controlled with the left 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
Select with RIGHT mouse button to affiliate with A2 cursor
Select with LEFT mouse button to affiliate with A1 cursor