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university:courses:alm1k:circuits1:alm-cir-9 [06 Oct 2018 16:12] – [Frequency response plots with ALICE Bode Plotter] Doug Merceruniversity:courses:alm1k:circuits1:alm-cir-9 [03 Nov 2021 20:18] (current) – [Activity: Band Pass Filters] Doug Mercer
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-======Activity 9: Band Pass Filters======+======Activity: Band Pass Filters, For ADALM1000======
  
 =====Objective:===== =====Objective:=====
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 The Band Width of frequencies passed is given by:  The Band Width of frequencies passed is given by: 
  
-<m>BW= f_L<f_H</m>+<m>BW= f_H-f_L</m>
  
 All the frequencies below f<sub>L</sub>and above f<sub>H</sub> are attenuated and the frequencies between are passed by the filter.  All the frequencies below f<sub>L</sub>and above f<sub>H</sub> are attenuated and the frequencies between are passed by the filter. 
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 <WRAP centeralign>Figure 1, Band Pass Filter circuit</WRAP> <WRAP centeralign>Figure 1, Band Pass Filter circuit</WRAP>
 +
 +From this previous lab on [[university:courses:alm1k:circuits1:alm-cir-lc-resonator|Parallel LC Resonance]] we can also use the formula for the LC resonance to calculate the center frequency of the band pass filter, the resonant frequency ω<sub>o</sub> is given by: 
 +
 +<m>ω_o = 1/sqrt{LC }</m> rad/s 
 +
 +OR 
 +
 +<m>f_o = 1/(2pi sqrt{LC})</m> Hertz
  
 **Frequency Response:** **Frequency Response:**
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 To show how a circuit responds to a range of frequencies a plot of the magnitude ( amplitude ) of the output voltage of the filter as a function of the frequency can be drawn. It is generally used to characterize the range of frequencies in which the filter is designed to operate within. Figure 2 shows a typical frequency response of a Band Pass filter. To show how a circuit responds to a range of frequencies a plot of the magnitude ( amplitude ) of the output voltage of the filter as a function of the frequency can be drawn. It is generally used to characterize the range of frequencies in which the filter is designed to operate within. Figure 2 shows a typical frequency response of a Band Pass filter.
  
-{{ :university:courses:alm1k:circuits1:alm-cir-lab9-fig1.png?500 |}}+{{ :university:courses:alm1k:circuits1:alm-cir-lab9-fig2.png?600 |}}
  
 <WRAP centeralign>Figure 2, Band Pass Filter Frequency Response</WRAP> <WRAP centeralign>Figure 2, Band Pass Filter Frequency Response</WRAP>
 +
 +{{ :university:courses:alm1k:circuits1:bpf_conn.png?500 |}}
 +
 +<WRAP centeralign>Figure 3, Band Pass Filter Connections</WRAP>
  
 ====Materials:==== ====Materials:====
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 1. Set up the filter circuit as shown in figure 1 on your solderless breadboard, with the component values R<sub>1</sub> = 1 KΩ, C<sub>1</sub> = 0.047 µF, L<sub>1</sub> =20 mH.  1. Set up the filter circuit as shown in figure 1 on your solderless breadboard, with the component values R<sub>1</sub> = 1 KΩ, C<sub>1</sub> = 0.047 µF, L<sub>1</sub> =20 mH. 
 +
 +{{ :university:courses:alm1k:circuits1:bpf_bb.png?500 |}}
 +
 +<WRAP centeralign>Figure 4, Band Pass Filter Connections</WRAP>
  
 2. Set the channel A AWG Min value to 0.5 and Max value to 4.5V to apply a 4Vp-p sine wave centered on 2.5 V as the input voltage to the circuit. From the AWG A Mode drop down menu select the SVMI mode. From the AWG A Shape drop down menus select Sine. From the AWG B Mode drop down menu select the Hi-Z mode. 2. Set the channel A AWG Min value to 0.5 and Max value to 4.5V to apply a 4Vp-p sine wave centered on 2.5 V as the input voltage to the circuit. From the AWG A Mode drop down menu select the SVMI mode. From the AWG A Shape drop down menus select Sine. From the AWG B Mode drop down menu select the Hi-Z mode.
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 Use the Start Frequency button to set the frequency sweep to start at 100 Hz and use the Stop Frequency button to the sweep to stop at 20000 Hz. Select CHA as the channel to sweep. Also use the Sweep Steps button to enter the number of frequency steps, use 100 as the number. Use the Start Frequency button to set the frequency sweep to start at 100 Hz and use the Stop Frequency button to the sweep to stop at 20000 Hz. Select CHA as the channel to sweep. Also use the Sweep Steps button to enter the number of frequency steps, use 100 as the number.
  
-You should now be able to press the green Run button and run the frequency sweep. After the sweep is completed ( could take a few seconds for 100 points ) you should see something like the screen shot in figure 3. You may want to use the LVL and dB/div buttons to optimize the plots to best fit the screen grid.+You should now be able to press the green Run button and run the frequency sweep. After the sweep is completed ( could take a few seconds for 100 points ) you should see something like the screen shot in figure 5. You may want to use the LVL and dB/div buttons to optimize the plots to best fit the screen grid.
  
-Record the results and save the Bode Plot using Save screen under the File drop down menu.+Record the results and save the Bode Plot using your favorite screen capture tool and include it in your lab report.
  
 {{ :university:courses:alm1k:circuits1:alm-cir-lab9-screen1.png?600 |}} {{ :university:courses:alm1k:circuits1:alm-cir-lab9-screen1.png?600 |}}
  
-<WRAP centeralign>Figure 3: Bode Analyzer Settings</WRAP>+<WRAP centeralign>Figure 5: Bode Analyzer Settings</WRAP>
  
 +To better understand the frequency characteristics of this parallel LC filter plot the low pass frequency response with just the capacitor (i.e. remove the inductor). Make the same frequency sweep and take a snap-shot of the gain ( CB-db - CA-dB ) and relative phase ( CA-CB ). Now plot the high pass frequency response with just the inductor (i.e. put the inductor back and remove the capacitor). The Bode plot in figure 6 shows these results. Note that the frequency where the low pass and high pass gain is the same and the relative phase sums to zero ( at about +70 and -70 degrees) is at the resonate frequency.
 +
 +{{ :university:courses:alm1k:circuits1:alm-cir-lab9-screen2.png?600 |}}
 +
 +<WRAP centeralign>Figure 6: Low and High pass response</WRAP>
  
 ====Questions: ==== ====Questions: ====
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 2. Graph the Frequency Response for each filter built in the lab. (Use the values recorded in the tabular column and graph with the frequency on a logarithmic scale). Compare this to the response obtained from the Bode Plot and comment.  2. Graph the Frequency Response for each filter built in the lab. (Use the values recorded in the tabular column and graph with the frequency on a logarithmic scale). Compare this to the response obtained from the Bode Plot and comment. 
 +
 +**Resources:**
 +
 +  * Fritzing files: [[downgit>education_tools/tree/master/m1k/fritzing/bpf_bb |bpf_bb]]
 +  * LTSpice files: [[downgit>education_tools/tree/master/m1k/ltspice/bpf_ltspice | bpf_ltspice]]
  
 **For Further Reading:** **For Further Reading:**
  
-[[university:tools:m1k:alice:desk-top-users-guide|ALICE Desk-top User's Guide]]+[[university:tools:m1k:alice:desk-top-users-guide|ALICE Desk-top User's Guide]]\\ 
 +[[http://circuitcalculator.com/lcfilter.htm|LC filter calculator]]
  
 **Return to Lab Activity [[university:courses:alm1k:alm_circuits_lab_outline|Table of Contents]]** **Return to Lab Activity [[university:courses:alm1k:alm_circuits_lab_outline|Table of Contents]]**
  
university/courses/alm1k/circuits1/alm-cir-9.1538835126.txt.gz · Last modified: 06 Oct 2018 16:12 by Doug Mercer

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