Introduction to PSpice

Introduction to PSpice Simulation Software 1

The Origins of SPICE In the 1960 s, simulation software begins CANCER Computer Analysis of Nonlinear Circuits, Excluding Radiation Developed at the University of California, Berkley Funded by United States public funds One of the first simulation software ever created was called CANCER. This is for Computer Simulation of Nonlinear Circuits Excluding Radiation. The exclusion of radiation was included in the name, because the thought was that the software would never be able to simulate radiation. The term CANCER was also a comment that the program would die without the external funding from the military or other institutions. The people at Berkley felt much different after they realized that the program was a great success. 2

The Origins of SPICE From CANCER to SPICE SPICE developed in the 1970 s Simulation Program with Integrated Circuit Emphasis Developed to save money Simulation of circuits, not physically building Transistor sizes Microprocessors vs. 2N2222 After the CANCER project, the next innovation was the SPICE program. SPICE stands for Simulation Program with Integrated Circuit Emphasis. This new acronym was created from the fact that many of the components being placed on the new integrated circuit were becoming smaller than the discrete components themselves. With this in mind, the SPICE creators wanted to save money by not having to manufacture chips to test the circuits. The next logical step was to let a computer do the testing for them. By not building the physical circuit, the designers can save a lot of time and money. 3

The Origins of SPICE From SPICE to SPICE2 SPICE 2 was in response to the wonderful acceptance of SPICE Comments, questions, and complaints found their way back to UC-Berkley SPICE 2 was released into the public domain This means its free to use in the United States Commercial versions that offer much more support and features In the mid 1970 s SPICE was upgraded to SPICE2. SPICE2 was in response to the feedback that Berkley was receiving. The folks at Berkley never wanted any of this information, but once they got it, it allows them to make the program better. In just a few short years, the SPICE software was able to create robust, powerful, and very general algorithms that are still the underlying principles of today s SPICE programs. The release of SPICE 2 into the public domain, made it free for use inside the United States. This holds true today even though there are commercial version of SPICE available. These versions offer customer support and special add-ons. This is what is being paid for if you had to purchase a copy of SPICE. Most copies of SPICE can be downloaded or available on CD for free. 4

That Was Then The original way of entering circuit information A text file with syntax specific to the simulator Easy to remember commands and syntax R Resistor C Capacitor L Inductor {Element} {node1} {node2} {value} Entered into any text editor with proper syntax When there was no such thing as windows, and all that was available was a text system, it was a little more complicated to set up the simulation. Today with all the Graphical User Interfaces available to computer users, that is not done as much anymore. This method would also require drawing (or having a drawing) of the entire circuit, so that some preliminary analysis could be performed, and then mapped to the text file. The element names for PSPICE are simple to remember for the passive elements, R, L, C. For some other commands, there is a different syntax that is used. 5

That Was Then The circuit above is shown in the text file to the right The simple 4 element circuit on the left would require the text file on the right. The ironic part of this comparison, is that the circuit was created with the Graphical User version of SPICE, and then the text file was typed out in Notepad as you can see. Notice that the.end and the cir file extension. Each of these are required for the file to work correctly with the software. 6

That Was Then This is a larger version of the text file from the last slide. Here I will talk about some of the lines that are in this text file. The first line of the file is the circuit name. The next line is a comment line that starts with an asterisk. The next line is the voltage source. Following that is the nodes that the element is connected to. Finally the value of the element is listed last. You can comment at the end of each line, by starting the comment with a semicolon. Lastly the.end is required to tell the simulator that is the end of the file. After simulation the program would give a file titled {title}.out. This is the output of the circuit and lists all the important information about the circuit, such as voltages and currents at each node and through each element. 7

New user interface Graphical circuit diagrams Variation of simulation parameters with a few clicks This Is Now The advances in Operating systems on computers gives program designers the freedom to make Graphical User Interfaces like that shown above. This makes the programming of the simulation simpler than that of the old days. The old days required the knowledge of the syntax of all the components along with all the different simulation calculations. Now a days, the circuit simulation results can be viewed with a click of a button, or with the placement of a few probes. To get the output graphs it takes a few changes in some of the settings, but that is a very simple task with the mouse. 8

First Look at Capture First window you will see when you open Capture Create a new Project File New Project This will open a new window First, we will want to open Capture from the start menu. The default installation directory may have been changed, so you ll want to look for something that indicates that CAPTURE or PSPICE. Then you will want to open the CAPTURE STUDENT Shortcut. This will open the window above. Next you will want to use the File -> New -> Project to create a new project. 9

New Project Window Select a project name PSpice Lab Simulation Select a project location C:\PSpice\{YourName} Select what type of project Analog or Mixed A/D Click OK This is the new window that you will get. First we want to type in a project name. Type in PSpice Lab Simulation into the Name field. The window will then look like this. The next step will be to find a location to save the project. You can either type in the path location or use the Browse button to find a location. If you use the browse button you can create a new folder with your name to save the lab. If you know the exact path of a file you want to save too, type this full path into the location field. The window will then look like this. Make sure that the Analog or Mixed A/D is selected then the last step is to click the OK button. 10

Create PSpice Project This window will open Select the bottom option Create a blank project Click OK This window is used to make projects from an already created project. This acts like a template and will allow many of the same projects to be made from one common project. In this window select Create a Blank Project and then click Ok. 11

The Project Windows The Main Project Window Two other information windows Session Log Window Project File Window Our main window Schematic 1: Page 1 This is the project workspace. This main window has three sub windows. The window on the left is titled Your Project Name. If everything was followed up to this point, it will read PSpice Lab Simulation. The next window on the far top right, is the session log window. This window will inform you of what is happening in your project session. For our purposes we will not need that window. The most important window in this screen is that of the circuit. It is titled Schematic 1: Page 1. This is where our part will be placed for the simulation. This is what makes PSpice now days better than the old days. 12

Place Parts Place the 5 resistors Using Place Part Type R in Part Field Place the Voltage Source Using Place Part Type Vdc in Part Field Right click and choose End Mode Now that we know where the parts are to be placed, we can start to place them. Click on the Schematic 1 window to make that the active window (just to show the point, you can click on the other windows and the menus will change). Next, use the Place, Part command, and in the Part field, type in R. This will select the Resistor part. Click on the OK button that appears and place 5 resistors. Repeat the Place, Part command, and in the Part field type in Vdc. This will select the DC Voltage source. Click the OK button and place the DC Voltage source. Right click and choose End Mode. 13

Rotate and Move Resistors Click on the resistor Use Ctrl+R to rotate Repeat for 4 resistors Move and place the resistors in parallel Change the values Double Click on the 1k and enter 4k of the parallel resistors Now we need to move the resistors so that they are arranged with one in series and 4 in parallel. This is done by clicking and dragging the resistors to the correct spot. But the resistors are in the wrong orientation, so we can fix that by clicking on a resistor and pressing Control+R. We can also do this by first selecting a resistor and then right clicking and choose rotate. Repeat this until the circuit looks like the following. Now we have to change the values of the resistors. This can be done by double clicking on the value of the resistor. The default value of the resistors are 1k. We want to change the four parallel resistors to 4k. After double clicking on the value type in 4k into the value field. Repeat for the four parallel resistors. 14

Change the Voltage and Wire Change DC Voltage Double Click on 0Vdc and enter 16Vdc Now wire the circuit Using Place Wire Click on one node, and draw to the other and click again Right click and select End Mode Next, we want to change the value of the DC voltage source. This is done in the same way that the values of the resistors were changes. Double click on the default value of 0Vdc for the power supply and enter 16Vdc. The next step is to wire the circuit. This can be done with the Place, Wire command. Placing wire is fairly easy. Click on one node of the circuit, and then draw to the other node. Once there, click the mouse again. Repeat until the circuit is completely wired as shown above. 15

Placing the Ground Every PSpice circuit must have a ground Use the icons on the right 9 th icon down This opens the Place Ground window Select the 0/Source Click OK The next step in the circuit is to place a ground. This is required for every circuit simulation in Capture or PSpice. If there is no ground, the simulation will give Node is Floating errors, and will not work. Use the Place Ground icon on the right side of the screen, and open the window above. Make sure that the Source library is in the Libraries field. If not, ask for help. Then select the 0/source ground, and click ok. Place the ground on the circuit near the bottom and then right click and choose End Mode. Then wire the bottom of the circuit to the ground using the Place, Wire command. The circuit should now look like the next slide. 16

The Completed Circuit This is the completed circuit. Notice that this is a very simple resistive circuit. When you do the prelab for this circuit you will be able to determine the voltages and currents. For now, we will go through the demonstration of how to run the simulation, but will withhold the results until lab time. 17

Simulation Profile Need to create a simulation profile PSpice New Simulation Profile Name the profile DC Solution Click OK The simulation profile is what allows us to vary how we can simulate the circuit. There are many different things we can change to make the simulation fit our needs. In this straight forward example we are just going to be working with the DC Solution, and all that is required is the Bias Point. So, type in a name for your Simulation Profile and make sure none is in the Inherit From box. Click OK to continue. 18

Edit the Simulation Profile Go to the Analysis Tab Under the Analysis type, choose Bias Point This is to find the DC solution Click OK Ready to Simulate Once the simulation profile window is open, take a look around at all the different options you can change. Make sure not to change anything right now though. We are interested in the Analysis tab which should be selected by default. Now choose Bias Point under the Analysis Type. This will get the DC Solution that we are looking for. Once this is done, you can click the OK button to return to the Schematic window. 19

Running the Simulation The last step is to RUN the simulation Do this by selecting PSpice Run After running the simulation a new window will open Close this window and return to the Schematic 1: Page 1 window Use the V and I (and maybe W ) icons on the top of the screen For finding voltages and currents (and power) Now that the simulation profile is set up, and the circuit is complete, we are now ready to run the simulation. You can do this by choosing the PSpice, Run command. This will open a new window that is not very useful for this simulation, so close that window. Now there are icons near the top of the screen that have V and I (and if the version is high enough, a W icon too). Once the simulation is complete, you can click these buttons on and off, to view the voltages at the nodes and the currents through the components. 20

Now You Know With this basic underlying knowledge Can change Resistor values Voltage supply values Resistor configuration Can learn More simulation parameters More components for simulation Time for Lab Good Luck Now that we have the basics of DC circuits down, we can change things up a little bit. We can vary the resistor values, the supply voltages and even how the resistors are connected. There is a lot of room to improve on this basic principle of resistor circuits though. You can look through the parts list to see what type of components are available. There are many digital chips and even more analog parts. So, in the future we can learn what the other parameters in the simulation profile can do and on top of that add more components like Capacitors, Inductors, Transistors, Diodes, and many other. Now that you have this basic knowledge, we can go off to lab and make use of this information. That is an introduction to PSpice, and you will use this program more in your Electrical Engineering careers. 21