Performance Analysis — Op-Amp Gain Bandwidth

The Performance Analysis capabilities of Probe are used to view properties of waveforms that are not easily described. Examples are amplifier bandwidth, rise time, and overshoot. To calculate the bandwidth of a circuit, you must find the maximum gain, and then find the frequency where the gain is down by 3 dB. To calculate rise time, you must find the 10% and 90% points, and then find the time difference between the points. The Performance Analysis gives us the capability to plot these properties versus a parameter or device tolerances. Hie Performance Analysis is used in conjunction with the Parametric Sweep to see how the properties vary versus a parameter. The Performance Analysis is used in conjunction with the Monte Carlo analysis to see how the properties vary with device tolerances. In this section we will plot the bandwidth of an amplifier versus the value of the feedback resistor. See Sections 9.B.3 and 9.E to see how to use the Performance Analysis in conjunction with the Monte Carlo analysis. 

Suppose that for the example of Section 5.F, we would like to see a plot of how the upper 3 dB frequency is affected by the value of the feedback resistor, Rf. This plot can be accomplished using the Performance Analysis capabilities of Probe. Repeat the procedure of Section 5.F. When you obtain the plot on page 310, you may continue with this section. The plot on page 310 is repeated as follows  

Before we look at the Performance Analysis we would like to create a new plot window. Select Window and then New Window. A second empty window will appear  

To plot the upper 3 dB bandwidth versus the parameter RFj/al we must enable the Performance Analysis. From the Probe menus select Plot and then Axis Settings. The dialog box shows the settings for the x-axis  

Under Processing Options we see that the square next to Performance Analysis does not have a checkmark in it, indicating that it is not enabled. To enable the Performance Analysis click the LEFT mouse button on the text Performance Analysis. The square should fill with a checkmark 0, indicating that the Performance Analysis is enabled  

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