Using a Bode Plotter on the passive component network alone, I saw what I was hoping to see: a sharp peak in the transfer function at the correct frequency-in this case at approximately 1.6 MHz. However, I wanted to look at the transfer function of the passive components just to make sure that I had everything right, and when doing that, I got into some trouble trying to get the Bode Plotter to function ( Figure 1).įigure 1 An unsuccessful analysis attempt. My circuit was a simple Colpitts oscillator and the simulation showed that it would indeed oscillate. We may try implementing a 2nd order filter to see if it helps at our next meeting.Using my Multisim SPICE tool to analyze an oscillator, I ran into a little bit of simulation trouble. Due to this, our group concluded that our filter design although it works for clean sine waves, is quite ineffective for isolating the different strings of a guitar (due to the shape of the input waveform). We examined the signal being input from the guitar and found that it hardly resembled a sine wave at all. Upon switching back to the guitar, again every string played through the speaker (although the higher strings were definitely quieter than the lower strings). Confused, we tried using the analog discovery and found again that only right around 110Hz was audible as expected.
![bode plot multisim bode plot multisim](https://media.cheggcdn.com/media/4d4/4d46a05e-39bc-4fed-847b-9d91a4f31dfd/phpXJYUrn.png)
We then fed the output of this circuit into our filter and were able to get an audible output through the speaker! The only issue we had now was that essentially every string would play through the speaker. This is accomplished by having an R2 that is ~2x that of R1 based on the figure below. After some experimentation, we settled on an amplifier with a theoretical gain of 3. If anyone else is ever using a fender 4 pin guitar jack, the output is pin 2 and ground should be connected to pin 1.Īfter resolving this issue, we found that the output voltage from the guitar was way to small to be fed directly into our filter (we were getting no measurable output), we resolved this by adding an amplifier at the beginning of the circuit to amplify the signal enough to feed into the filter. After trying all possible combinations, we were able to determine this. The part came with no documentation whatsoever so it required a process of experimentation to determine which pin needed to be connected to ground and which pin was the output from the guitar.
#BODE PLOT MULTISIM HOW TO#
Our first problem was figuring out how to use the 4 pin jack we had purchased. Yesterday we were able to test our circuit with an electric guitar to see if our filter worked as well for the frequency output of the string compared to a nice clean sine wave from the function generator. Although this picture was included before, here is our setup from that day of testing: After testing with the guitar, however, we soon discovered this was not the case. Since this two closest notes are at ~82.41Hz and 146.83Hz, we figured our circuit had accomplished the desired goal of isolating our single note. Hooking it up to the speaker, we found that for a decent volume at 110Hz, the output became nearly inaudible at ~90Hz and ~130Hz.
![bode plot multisim bode plot multisim](https://holooly.com/wp-content/uploads/2021/01/6-25-1.png)
This was very similar to the theoretical bode plots we generated through multisim. Using the oscilloscope, we determined our peak output occurred right around 110Hz as desired and our 3dB frequencies occurred around ~120Hz and ~105Hz. Our circuit actually seemed to work quite well in our testing. We decided to try adding another amplifier (with a theoretical gain of 2) after the filter and connected the speaker to its output. The output voltage essentially would never change in this configuration.
![bode plot multisim bode plot multisim](https://cnx.org/resources/869ffba815301d058cd8b2da9bb1d46949f3b5e6/Graphic4.png)
![bode plot multisim bode plot multisim](https://instrumentationlab.berkeley.edu/sites/default/files/Multisim/image002.jpg)
Originally, we connected our speaker directly to the output of the filter, but this completely ruined the desired intent of the circuit. One very important alteration to our circuit was the addition of another amplifier after the filter.
#BODE PLOT MULTISIM GENERATOR#
A few pictures were posted earlier from this day, but to sum things up: We built our circuit, hooked it up to a function generator in the circuits lab room and hooked the output up to a speaker in order to see how we did. It should be noted that we were able to test our circuit design last week and verified that its actual behavior was very similar to the theoretical behavior we saw on multisim. Our group met again yesterday (as you can likely see from the video and images posted recently) and we finally were able to test our circuit using the guitar!