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Introduction to Multisim: Learn to Capture, Simulate, and Layout in Less Than 30 Minutes
Publish Date: Sep 02, 2014
Overview
NI Multisim is a powerful schematic capture and simulation environment that engineers, students, and professors can use to simulate electronic circuits and prototype Printed Circuit Boards (PCBs). This article shows you how to capture,simulate, and layout your first design in Multisim.
The example circuit in the article is an amplifier circuit. This non-inverting operational amplifier configuration consists of one active component (the operational amplifier) and two passive resistor components that will be used to complete the feedback network to provide gain in this circuit.
Table of Contents
Introduction Part A: Selecting Components Part B: Wiring the Schematic Part C: Simulating the Circuit Part D: Transferring to PCB Layout Part E: Routing the Board Additional Resources
1. Introduction
For this introductory example, you will simulate a standard non-inverting operational amplifier circuit (shown in Figure 1). The gain of this non-inverting amplifier is calculated by the expression Gain = 1 + R1/R2. Therefore, if R1 = R2, then the gain is equal to 2 , which you will verify when you run interactive simulation in Multisim.
Figure 1. Non-inverting amplifier circuit.
2. Part A: Selecting Components
Begin by drawing your schematic in the Multisim environment. Open Multisim by selecting All Programs»National Instruments»Circuit Design Suite 13.0»Multisim 13.. Select Place»Component. The Select a Component window appears (also known as the Component Browser ), as shown in Figure 2.
Figure 2. Select a Component window. The Component Browser organizes the database components into three logical levels. The Master Database contains all shipping components in a read-only format. The Corporate Database is where you can save custom components to be shared with colleagues. Finally, the User Database is where custom components are saved that can be used only by the specific designer.
Additional Points The components (or parts) are organized into Groups and Families to intuitively and logically group common parts together and make searching easier and more effective. The Component Browser shows the component name, symbol, functional description, model, and footprint all in a single popup. Select the Source s Group and highlight the POWER_SOURCES family. Select the GROUND component (as shown in Figure 2). Click OK. The Select a Component window temporarily closes and the ground symbol is ‘ghosted’ to the mouse pointer. Move the mouse to the appropriate place on the workspace and left-click once to place the component. After placing the component, the Select a Component window will open again automatically. Go to the Sources Group again and highlight the POWER_SOURCES Family (if not already highlighted from the previous selection). Select the DC_POWER component. Place the DC_POWER component on the schematic. Repeat steps 7, 8 and 9 to place a second DC_POWER component.
Additional Points Without a power and ground your simulation cannot run. If you need multiple components you can repeat the placement steps as shown or place one component and use copy (Ctrl+C) and paste (Ctrl+V) to place additional components as needed. By default, the Select a Component window keeps returning as a pop-up until you have completed placing your components. Close the window to return to the schematic entry window.
Now place the remaining circuit components using the techniques discussed in the previous steps. Select the Analog Group and the OPAMP family. Type AD712 in the Component field. Select the AD712SQ/883B component, as shown in the next figure:
Figure 5. Wiring the schematic. The last key step is to connect the power supply terminals to the positive and negative power rails of the opamp via a virtual connection using On-page connectors. Select Place»Connectors»On-page connector and connect it to the positive terminal of the V1 power supply. The On-page Connector window will open. Enter +V in the Connector name field and click OK. Select another On-page connector and connect it to terminal 8 of the opamp. The On-page Connector window will open again. Select the +V connector in the Available connectors list and click OK. The positive terminal of the V1 DC power supply is now connected to pin 8 of the opamp via a virtual connection. Repeat steps 6 to 9 to connect the negative terminal of V2 to pin 4 of the opamp. Name the On-page connector –V. The schematic should now look like the following figure:
Figure 6. Schematic with On-page connectors.
4. Part C: Simulating the Circuit
You are now ready to run an interactive Multisim simulation; however, you need a way to visualize the data. Multisim provides instruments to visualize the simulated measurements. Instruments can be found on the right menu bar and are indicated by the following icons.
Figure 7. Instruments toolbar. Select the Oscilloscope from the menu and place this onto the schematic. Wire the Channel A and Channel B terminals of the Oscilloscope to both the input and output of the amplifier circuit. Place a ground component and connect it to the negative terminals of the Oscilloscope. Right-click the wire connected to Channel B and select Segment color. Select a shade of blue and click the OK button. The schematic should look like Figure 8.
Figure 8. Connecting the Oscilloscope to the schematic. Select Simulate»Run to start the simulation. Double-click on the Oscilloscope to open its Front Panel and observe the simulation results (see Figure 9). As expected, the input signal is being amplified by a factor of 2. Stop the simulation by pressing the red stop button in the simulation toolbar.
Figure 9. Simulation results.
5. Part D: Transferring to PCB Layout
We are now ready to transfer the Multisim design to Ultiboard for PCB layout. In preparation for this we need to take into consideration that sources (power, signal) and ground are virtual components, therefore, they cannot be transferred to Ultiboard. Also, all components must include footprint information. It is a good practice to replace power sources and ground with connectors. Remove V1 V2 V3 , , and the Oscilloscope from the schematic. Do not remove the On-page connectors. Open the Component Browser , and place the 282834-4 terminal block from the Connectors Group, TERMINAL_BLOCKS Familly. This connector will be used to connect the power supplies ( +V -V , ). Connect pin 1 of the connector to the +V On-page connector, pin 4 to the –V On-page connector, and pins 2 and 3 to ground, as shown in the next figure:
Figure 13. Design Toolbox. The Layers tab of the Design Toolbox is where you move between layers of your design and control the appearance of layers. Go to the toolbar area and locate the Select toolbar, refer to the following figure.
Figure 14. Select toolbar. The Select toolbar contains the functions used to control selection filters. In other words, these filters control what can be selected by the mouse pointer. Disable all the filters except Enable selecting other objects. Double-click the board outline on the workspace area to open the Rectangle Properties window. Select the Rectangle tab, change Units to inch and enter 2 for Width and 2 for Height. Click OK.
6. Part E: Routing the Board
Place components inside the board. Go to the Select toolbar and disable all the filters except Enable selecting parts. Drag part J2 and drop it inside the Board Outline. You can rotate parts by using the <Ctrl+R> shortcut. Place the rest of the parts inside the Board Outline, use Figure 15 as guidance.
Figure 15. Parts placement. For this exercise you will place traces on both, the Copper Top and Copper Bottom layers. Double-click the Copper Top layer in the Design Toolbox. Select Place»Line. Locate part U1 (the opamp). Note that pin 1 needs to be connected to R1, as indicated by the ratsnest. Click pin 1 of part U1 , draw a line to R1 and click its pin to finish the trace. Press Esc to exit the routing mode. The trace will look like the following figure:
Figure 16. Placing a trace. Double-click the the Copper Bottom layer in the Design Toolbox. Select Place»Line. Click pin 2 of part U1 , draw a line to R1 and click its pin to finish the trace. Press Esc to exit the routing mode. Note that the color of the trace is red, which is the color configure for the Copper Bottom layer. Finish placing traces for the rest of the connections. Your board should look like Figure 17.
Figure 17. Routed board. Select View»3D Preview to open a 3D view of your design, as show below.
