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Butterworth Filter By Featuring an AC Analysis Using Multisim Properly

In a previous post I mentioned the wide variety of Advanced Analysis SPICE available to Multisim, and also saw how to run a Transient Analysis .

At this time we will characterize a low pass Butterworth filter of fourth order using CA Analysis in Multisim. The following figure we can see the filter to characterize:

This circuit is based on three operational amplifiers LM124AE has a cutoff frequency of 500 Hz and a gain of 10 (20 db .) This circuit was taking the book Electric Circuits, Seventh Edition, Nilsson / Riedel.

referenecia As this circuit you can download by clicking here step and join the Academic Community NI .

Once you have run the simulation circuit ng and open the front panel of the oscilloscope . We can see that with a power input of 1 Vp to 250 Hz have an amplified output of 10 Vp

experiment changing the frequency of AC power at 600 Hz:

As we can see the output of the circuit begins to fade, which is expected given the cutoff frequency of 500 Hz

Now let's configure a CA analysis in Multisim to know the frequency response of Butterworth filter. In my edition of Multisim in English 'm going to simulate menu>> An Alisis >> An Alisis be AC \u200b\u200b... Configuration window opens AC Analysis. In the Settings tab often we'll select the following:

Basically we are setting a frequency sweep from 1 Hz to 10 kHz. Note that you can select different types of scanning, the number of points in the sweep and the vertical scale.

Now let Output tab and select V (vout) as the variable selected for analysis. To add V (vout) to this list only have to search for and select Variables column circuit and to click the Add button :

In the window Analysis of CA have two more tabs: Options analysis and summary . The Scan Options tab contains default settings for Multisim SPICE simulation, for example, error tolerances, operating temperature, etc. We recommend leaving the default settings as they work well for most simulations we perform. Finally, the Summary tab find a list of how we set the AC Analysis in Multisim.

CA's run the analysis by clicking the button Simulate . The Grapher view opens and displays the Magnitude and Phase of our low-pass Butterworth filter of fourth order:

From the figure we see that as expected, approximately 500 Hz the magnitude starts to decline. using the cursor can take more accurate measurements as shown below:

We conclude that CA analysis is a powerful tool when we want to calculate the frequency response of a circuit, and do it in Multisim is easy. If you have any questions do not hesitate to place it in the comments section.

Thanks and greetings!

Fernando