Essay ECET 350 Topic 1 Complete DeVry
ECET 350 Topic 1 Complete DeVry
ECET 350 Topic 1 Discussion
WEEK 1: ACTIVE FILTER DESIGN PARAMETERS
What are the features you would consider essential if you were designing your perfect amplifier? Define the values for parameters, such as input resistance, output resistance, and voltage gain.
WEEK 1: ACTIVE FILTER COMPONENT CHOICES
Give a thorough discussion about why you chose a certain value for your perfect amplifier parameter (one of input resistance, output resistance, and voltage gain only).
ECET 350 Topic 1 Lab 1 Sallen-Key Active Filter Design
Objectives
- Design and simulate a Butterworth, low-pass Sallen-Key active filter
Tools Needed
- Multisim Software
Introduction
Active filters are key elements in both analog and digital signal processing. In this lab, you will first design, and using Multisim, simulate a Butterworth type, Sallen-Key low-pass filter comparing the design specifications against the simulation. Next, you are to actually construct the designed Butterworth and test its response measured against the design specifications, noting any differences between the simulated filter and the actual filter.
Answer all questions, complete all tables, and paste all figures and graphs in the Week 1 Lab Cover Sheet here (Links to an external site.) .
Submit your Week 1 Lab Cover Sheet.
You can also download the Week 1 Cover Sheet for the Week 1 Lab in the Files section of the Course Menu.
Multisim and Excel
Access the software at https://lab.devry.edu (Links to an external site.).
In this part, you will design an active low-pass filter with the following specifications.
Second-order low-pass filter, 3-dB ripple at the cut-off frequency of 3 kHz, type: Butterworth, circuit topology (VCVS): low-pass Sallen-Key circuit
The second-order, low-pass prototype for Butterworth type is given as
HP(s)=Hos2+1.4142s+1HP(s)=Hos2+1.4142s+1where
HoHois DC gain to be determined, and the cut-off frequency
ωC=2π.3000ωC=2π.3000rad/s.
1. Determine the transfer function using low-pass to low-pass transformation:
s=sωCs=sωC. Include your answer in the Lab cover report and from the transform function, identify the b0 and b1 coefficients.
H(s)=H(s)=bo=bo=
b1=b1=Choose the second-order, Sallen-Key low-pass filter shown in Figure 1.
Figure 1: Second-Order, Sallen-Key Low-Pass Filter
Based on circuit analysis, the circuit transfer function of the Sallen-Key low-pass filter shown in Figure 1 is given below.
G(s)=VoutVin=Gbos2+b1s+boG(s)=VoutVin=Gbos2+b1s+boWhere
G=1+R4R3,bo=1R1R2C1C2G=1+R4R3,bo=1R1R2C1C2b1=1R1C2+1R2C2−R4R2R3C1b1=1R1C2+1R2C2−R4R2R3C1To solve for circuit parameters, one of the solutions could be determined using the following conditions.
C1=C2=0.01μFC1=C2=0.01μFand
R1=R2R1=R2.
2. By matching coefficients of the Butterworth filter transfer function,
H(s),H(s),with the Sallen-Key circuit transfer function
,G(s),G(s), the design formulas are found below. Calculate values for the circuit parameters, and include your answers in the Lab cover report.
R1=R2=√1boC1C2=R1=R2=1boC1C2=For a Butterworth response, the ratio of
R4R3R4R3may be set at 0.586. If R3 is selected to be 10 kΩ, calculate the value for R4 and copy all calculation and values for R1, R2, R3, and R4 in the Week 1 Lab cover report.
R1=R2=R3=R4=R1=R2=R3=R4=3. Calculate the theoretical filter gains, and complete the calculated entries in Table 1 in the Lab cover report for verification. Note: The pass band ripple, Ap, for this type of Butterworth filter you may assume is approximately 3 dB.
Ho=G=1+R4R3=G(dB)=20logG=Ho=G=1+R4R3=G(dB)=20logG=ϵ2=10Ap(dB)10−1=ϵ2=10Ap(dB)10−1=MC=Ho√1+ϵ2=MC(dB)=20logMC=MC=Ho1+ϵ2=MC(dB)=20logMC=Roll-off rate:
RR≅−20N=RR≅−20N=(dB/decade) where N is the order of the filter.
Where
G(dB)G(dB): the filter DC gain
MC(dB)MC(dB): the gain at
ωCωC(radians/sec)
ωCωC: the cut-off frequency
APAP: the passband ripple (dB)
HoHo: the filter passband gain
RRRR: the roll-off rate (dB/decade)
4. Use MultiSim to simulate the designed Sallen-Key circuit and verify DC gain, gain at the cutoff frequency, and roll-off rate from the Bode plotter. Copy the Multisim schematic of your filter, and paste it into the Week 1 Lab cover report. Next, copy the steady state frequency response from the Bode-plotter, and paste it into the Week 1 Lab cover report, as well.
Complete the measured entries in Table 1 in the Week 1 Lab cover report.
Note that for the low-pass filters, the estimated roll-off rate is
RR(dbdecde)=G1(dB)−G2(dB)logf1−logf2=G1(dB)−G2(dB)log(f1f2)RR(dbdecde)=G1(dB)−G2(dB)logf1−logf2=G1(dB)−G2(dB)log(f1f2)where
G1G1at frequency
f1f1and
G2G2at frequency
f2f2are two measured gains beyond the cutoff frequency. You may also want to modify the Bode output window to record measurements over a wider range of frequencies and magnitudes.
Figure 2: Multisim Example of Filter Simulation—Values Are Not Correct for This Lab
ECET 350 Topic 1 Course Project
TEAM FORMATION
The class will be organized into teams with 3-4 students per team. In Week 1, you will work on team formation and selection of the focus of the course project. Week by week, you will work as a team to build out the final course project deliverable due in week 7. Note! All teams must be approved by the instructor.
See the Course Project Overview in Introduction and Resources.
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