Circuit designers use circuit simulation software packages to determine the operation of a circuit. The software allows testing of various designs without having to buy the hardware or physically build the circuit, thereby saving time and money. Of course, the results from a circuit simulation are only as accurate as the device models that are used in the software.

This lab is an introduction to a particular circuit simulation software package called SPICE (Simulation Program with Integrated Circuits Emphasis). In particular, we will use PSpice, which is a version of SPICE that runs on PCs. We will also set up some simple circuits in order to review the operation of the instruments in the lab.

Please bring your textbook, class notes, and breadboard to all lab sessions.

The following online PSpice resources are available for reference. (Although these refer to earlier versions of the software, most of the steps are the same in the latest version.)

• Tutorial from Bucknell's ELEC 463, 2006
• PSpice with Capture references from UPenn (see "Quick Reference Guide" and "Tutorial"):
  http://www.seas.upenn.edu/~jan/spice/spice.overview.html
• Concise and useful tutorial from Laurier Univ.

1. Start OrCAD Capture (Cadence -> Release 16.5 -> OrCAD Capture). We do not need the CIS option, although it does not hurt if you include it.
2. Click menu New -> Project, give it a Name and Location (folder), and be sure to select "Analog or Mixed A/D" then "Create a blank project" on the next pop-up.
3. Build your circuit in the Schematic window by first clicking Place -> Part. Always add a Ground (0/CAPSYM works well, and there is an icon for ground components). You may need to add three libraries (click the folder icon under the "Libraries:" block): analog.olb, opamp.olb, source.olb
   The libraries are in the folder ...\tools\Capture\library\pspice
4. Click menu PSpice -> New Simulation Profile and give it a name (usually the same name as the project). On the Analysis tab, set the Analysis Type (we will use Bias Point and DC Sweep today).
5. Click menu PSpice -> Run to run the simulation.

Please use PSpice to simulate two circuits: the voltage divider in Figure 2-41 on p. 69 of the textbook, and the op amp circuit in Figure 1-20 on p. 26.

• For the voltage divider, perform a "Bias Point" analysis. Use VDC for the voltage source. Try adding a "net alias" called V2 at the node between the two resistors. Use PSpice to find the voltage, current, and power of all elements (select the V, I, and W tools in the toolbar), and check the results with analysis.
• For the op amp circuit, create two different PSpice projects for Figure 1-20 parts (a) and (b). For the Analysis type, choose DC Sweep of the voltage source (name it VS) from -15 V to +15 V with increments of 0.1 V. Add a net alias called Vout at the op amp output terminal, and also add a voltage probe at Vout.
  • For (a), use an LM741 op amp and power it with -10 V and +10 V. It is convenient to use net aliases to connect the op amp power sources to the V+ and V- terminals.
  • For (b), a voltage-controlled voltage source (VCVS) is needed, and use gain A=100,000. Dependent sources are indicated in PSpice with the symbols E, F, G, and H (in the ANALOG library), corresponding to the cases in Table 1-3 on p. 25 of our textbook: E=VCVS, F=CCCS, G=VCCS, H=CCVS.
  With an ideal op amp, the output voltage is -2 times the source voltage. How do simulation results of Figure 1-20(a) and (b) compare with the ideal?

Set up the voltage divider circuit (required) and op amp circuit (if you have time) on your breadboard, then perform measurements that correspond to the simulations.

Here are a few tips to keep in mind when using PSpice:

• VDC is a DC source.
• When you start a new circuit, close your previous projects and open a new project for the new circuit.
• MEG=10⁶ and M=10^-3 (milli)
• For op amp circuits, be careful with + and - inputs, and use "mirror vertically" to flip the op amp terminals.

Please record your results and notes about using PSpice in your lab notebook. No report is required for this laboratory, but please demonstrate each circuit (simulated and experimental) to the instructor or lab assistant. You should save the PSpice files from this lab for future use in this course.

Thank you.