Performing Analyses on Your Circuit

This outlines basic information on using Multisim 2001analyses and explains how to perform one such analysis on your circuit.

The Analyses

Multisim provides you with many different types of analyses. Each one includes step-by-step instructions, provided on-line, to guide you through its use.

When you perform an analysis, the results are displayed on a plot in the Multisim Grapher (unless you specify otherwise) and saved for use in the Postprocessor.

When you choose most analyses from the menu that appears after you click the Analysis button in the Design Bar, you see a screen with several tabs, including:

• the Analysis Parameters tab, where you set the parameters for this particular analysis

• the Output Variables tab, where you specify which nodes are to be analyzed and what is to be done with the results

• the Miscellaneous Options tab, where, if you wish, you can choose a title for the plot, as well as other options

• the Summary tab, where, if you wish, you can see a consolidated view of all the settings for the analysis.

About Transient Analysis

In the Multisim User Guide, each analysis is described in detail, including the theory behind what Multisim does to perform the analysis. It is not necessary that you understand this information, which is provided primarily for the sake of completeness. In transient analysis, also called time-domain transient analysis, Multisim computes the circuit’s response as a function of time. Each input cycle is divided into intervals, and a DC analysis is performed for each time point in the cycle. The solution for the voltage waveform at a node is determined by the value of that voltage at each time point over one complete cycle.

Running the Analysis

! To ini tiate the analysis, click the Analysis button from the Design Bar and choose Transient Analysis from the pop-up menu. The simplified Transient Analysis screen appears, offering four tabs. To view the full screen with all the options and information displayed, as in the example shown below, click More.

The Miscellaneous tab offers options that provide you with additional flexibility, but that are not required. Use this tab to set a title for the analysis results, to check if the circuit is valid for analysis and to set custom analysis options.

The Summary tab offers a quick overview of all the various settings for your analysis. It is not required, but you can use it to view summary information about your analysis once it is complete. To perform the analysis, you have to set values on the other two tabs.

Step 1: Choose Output Variables

We are going to want to perform the Transient Analysis on nodes 3 (between Q1 and Q2) and 6 (from pin 3 of the gate). Choose those nodes from the available nodes on the Output Variables tab.

Note If you are still using your circuit, your node numbers may not match the ones above (node 3 and 6). This is likely a result of your circuit being wired correctly, but in a different sequence from the steps we suggested for the tutorial circuit. You can choose to continue to use your circuit and select the appropriate node numbers for the equivalent place in your circuit, or load tut3.msm from the Tutorial folder.

! To select the nodes:

1. Select 3 from the Filter variables displayed and click Plot during simulation.

2. Select 6 from the Filter variables displayed and click Plot during simulation.

The results look like this (if your screen doesn’t look like this, click More):

Step 2: Set the Analysis Parameters

Analysis parameters are set on the first tab as shown earlier in the chapter, and for our circuit can remain at their default values.

Step 3: View the Results

! To see the results, click Simulate. You see the following display:

The results show how the capacitor (the blue line) charges as a result of the spikes in the red lines.

! To see a key to the line color, click the legends button.

Note The Grapher window shows two tabs—one for the analysis you just ran, and one for the results of the simulation you ran in the previous chapter and viewed using the oscilloscope.