B. Muthuswamy and B. Boser EECS Department, UC Berkeley [email protected] Summer 2007 SPICE / MultiSim Tutorial 1. Introduction Cellular phones and computers are just two examples of some of today's extremely complex electronic systems. Such devices contain millions of circuit components, and simple trial and error is not an effective way of ensuring that the final product will work properly. As a result, designers often use circuit simulators to verify the performance of a circuit before fabrication. The most popular component level circuit simulator available today is called SPICE (Simulation Program with Integrated Circuit Emphasis), which was developed here at the University of California, Berkeley, in the 1970s under the guidance of Prof. Pederson. Today vendors offer many different versions of SPICE that differ mainly in the user interface but are internally very similar to the original “Berkeley SPICE”. This tutorial introduces a version of SPICE called MultiSim. Circuit simulation with SPICE (and MultiSim) involves two steps: (1) Enter in the circuit schematic (with MultiSim's graphical user interface). (2) Choose the type of analysis and run the simulation. 2. Organization of this Tutorial 1. Introduction 2. Organization I Basic Circuit Simulation Techniques in MultiSim 3. MultiSim Environment 4. Schematic Capture of an Example Circuit 5. Simulation and Results Display II Alternative Forms of Circuit Simulation in MultiSim. 6. Simulated Instruments 7. Using the Breadboard Tool 8. Conclusion Notes about this Tutorial: • Before running a simulation, you should always have a general understanding of how your circuit works. • In this document, Boldface black refers to actions you perform on the computer. Example: Click on the menu item.B. Muthuswamy and B. Boser EECS Department, UC Berkeley [email protected] Summer 2007 3. MultiSim Environment 1. First, you need to log into a lab machine to use MultSim. Ask the TA in-charge for login information. You may also be able to use MultiSim by logging in remotely. 2. Once logged in, Double-click on the icon on the desktop. If a window appears with “Evaluation License” written in the middle of it, click the Evaluate button. After MultiSim finishes loading, you should see the screen shown below in Figure 1. This is called “Capture and Simulate” environment because you “Capture” your schematic by drawing it in MultiSim and then you “Simulate” it. Figure 1 also shows the different parts of the MultiSim workspace; the location of the toolbars in your MultiSim window may be different. Figure 1 The most important components in the MultiSim workspace The purpose of each toolbar will become clear as you move through this document. If you don’t see the toolbars shown above, click on the View menu and go to Toolbars. Make sure that you at least have the toolbars shown in Figure 2 checked.B. Muthuswamy and B. Boser EECS Department, UC Berkeley [email protected] Summer 2007 Figure 2 Viewing the toolbars 4. Schematic Capture (Entering a Simple Circuit) To begin, let’s construct the simple circuit shown below in Error! Reference source not found.. This circuit is composed of a voltage source (battery), a resistor, and a potentiometer (variable resistor).B. Muthuswamy and B. Boser EECS Department, UC Berkeley [email protected] Summer 2007 Figure 3 A simple circuit captured in MultiSim I Adding the Voltage Source (Battery): 1. Click on the Power Source Family in the Virtual Toolbar. 2. The Power Source Components will pop up. 3. Click on the DC Power Source icon and then click on the workspace to place a battery. Error! Reference source not found. shows the result. Figure 4 A DC power source in MultiSim To change the value of the power source, Double-click the battery. This opens up the Power_Sources dialog box shown below. Make sure that the voltage is set to 12 V and then press OK.B. Muthuswamy and B. Boser EECS Department, UC Berkeley [email protected] Summer 2007 Figure 5 Power Sources Dialog box. Use this to change the value of the battery voltage. II Adding the Resistor and the Potentiometer 4. Click the Basic Components Family in the Virtual Toolbar. 5. The Basic Components will pop up. 6. Click on the Virtual1 Resistor tool and drag a resistor onto the workspace. Like the battery, you can double-click the resistor to change its properties. 7. Lastly, we must add the potentiometer. In the Basic Components window, click on the Potentiometer Tool and drag a potentiometer onto the workspace. You can increase/decrease the resistance on the potentiometer by pressing ‘a’ / ‘Shift+a’ on the keyboard. The increase and decrease refers to the resistance between the middle leg and the bottom leg of the potentiometer. You can also double-click the potentiometer to open its properties and change the total resistance of the potentiometer or its increment / decrement value. Error! Reference source not found. shows the circuit components placed on your workspace. The “50%” next to the potentiometer means that the resistance between the middle leg and bottom leg is 50% of 1 kΩ: 500 Ω. If you press ‘a’, the resistance will increase by 5% (the resistance between the middle leg and the top leg will decrease by 5%). Again, you can Double-click the potentiometer to change the increment percentage. If you move your mouse over the potentiometer, you can also use the slider that appears to change its resistance. 1 MultiSim distinguishes “Virtual” components from “Real” components. With real components, you place a part that has the actual shape of the real component, not a schematic symbol. You will see examples of this in Section 8.B. Muthuswamy and B. Boser EECS Department, UC Berkeley [email protected] Summer 2007 Figure 6 The circuit components are in place III Adding the Ground 8. The final component to add is the ground. You cannot simulate the circuit without a ground, because SPICE (the underlying simulation engine) uses nodal analysis to solve circuits. The first step in nodal analysis is to pick a ground node. It does not matter where we ground the circuit, but for consistency, let's pick the node at the bottom of the circuit as ground. 9. Click the Ground tool in the Power Source
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