ESE 331 Design Project – Filter Design Fall 2010

1. Design Project – The final project is a design of a non-inverting higher order active filter. You will design and calculate (using the equations in Chapter 16 of Sedra1 and Matlab (Tutorial)) the amplitude/frequency response (Bode Plot) for a Butterworth and Chebyshev filter that exceeds the specifications given below. Then select the better (in this case fewer op-amps) of the 2 designs and simulate it using PSpice to verify that the Bode Plot matches the Matlab calculations. Then you will build it in the lab using the solderless breadboards and the LF347 op amps and measure the amplitude/frequency response of the circuit and verify that it matches the Bode Plot from Matlab. At the end of the project you should have 3 Bode Plots that all match.

Filter Specifications as described in Sedra/Smith, “Microelectronic Circuits, 6th Edition”, Figure 16.3 DC Gain 20 dB Amax 3 dB Amin 60 dB Group 1 2 3 Fp (KHz) 5 7 9 Fs (KHz) 37 50 60

Fill out the table below to compare the Amplitude Response measurements.

Frequency Butterworth Butterworth Chebyshev Chebyshev Chebyshev Chebyshev

(KHz) Amplitude

(dB) Amplitude

(dB) Amplitude

(dB) Amplitude

(dB) Amplitude

(dB) Amplitude

(dB)

Sedra Eq. 16.11 Matlab

Sedra Eq. 16.18,16.19 Matlab PSpice Hardware

Fp/10 Fp (Fp+Fs)/2 Fs

2. Project Overview: a. Transfer Function Design - Using the equations from Sedra, define the

filter transfer functions (Butterworth and Chebyshev) for the lowest order filter that exceeds the specifications. By exceeds, it is meant that the attenuation at Fs is at least 60 dB. Use Matlab to obtain the Bode plot (magnitude versus frequency) from 1Hz to 1MHz for both filters and verify that your filters meet the specifications. Check the plot against equations 16.11, 16.18 and 16.19 in Sedra at the frequencies in the above table to verify that the Bode Plot is correct. Plot the Chebyshev and Butterworth responses on the same graph and compare them. Also using Matlab, plot the step responses. Present these results to the instructor. Make sure that all plots are well labeled!

b. Schematic Diagram – Using OrCAD (Download,Tutorial), draw the circuit to implement the “better” of the 2 designs. Simulate this circuit using PSpice (Tutorial here) (AC Sweep and Step Response) and compare to your Matlab results for your selected design. Make sure to use the “OPAMP” model from the Analog library for the simulations.

c. Circuit Construction and Test - Construct the filter circuit using the breadboards and retain them in your locker in Bryan 306. Some prototyping may be necessary to understand the best way to connect components. Once your circuit is complete and seems to be operating, do preliminary testing and compare results to those obtained using PSpice. Once you have satisfactorily debugged your circuit, test it carefully and record enough data to make a complete Bode plot to prove that it meets the requirements defined above. Obtain data comparable to that obtained in steps (a) and (b).

d. Filter Demonstration. Demonstrate the filter to the class on the designated date.

e. Report. Submit a report documenting the design process and test results. Include a list of materials (resistors, capacitors, and operational amplifiers) and an estimated cost per circuit for a quantity of 1000 filters. Include printed circuit board cost, but not labor costs.

Due Dates:

Report, prototype model, and presentation to the class are due 12/13/2010. References: 1. Adel S. Sedra and Kenneth C. Smith, Microelectronic University Press, New York, New York, 2010, 6th edition.

3. Design Steps

a. Determine the lowest order of Butterworth and Chebyshev filters that satisfy or exceed the specifications. *

b. Define the filter transfer functions using the equations from Sedra. * c. Calculate the magnitude of the transfer functions for both filters at the

frequencies in the table using equations 16.11, 16.18 and 16.19 in Sedra and enter these values in the table. *

d. Use Matlab to obtain the Bode plots (magnitude and phase) versus frequency from 1 Hz to 1 MHz for both filters verify that these magnitudes agree with the values in the table.

Use Matlab to obtain the time response of both filters to a step function input. *

e. Choose the filter that is simpler (lower order). Determine a circuit that uses ideal op amps , resistors and capacitors that will provide the required transfer function. * Determine the values of the circuit elements. Simulate the circuit with PSpice. Use PSpice to obtain Bode plots for the filter and verify that these magnitudes agree with the values in the table. Use PSpice to obtain the time response of the filter to a step function input and verify that it agrees with the response obtained with Matlab. * f. Construct the filter circuit from the schematic using a solderless

breadboard, LF347 op amps and other circuit elements. * Photograph the circuit board. Test the circuit to obtain frequency response data and use the data to make Bode plots for the filter and verify that these magnitudes agree with the values in the table. Test the circuit to obtain the time response of the filter to a step function and verify that it agrees with the response obtained with PSpice. * g. Estimate the cost of materials for a quantity of 1000 filter circuits. Include

the cost of the circuit board but no labor cost. * Please have your work checked and initialed by the instructor and before continuing.

4. Design Report Prepare a group report that includes: Cover page including group number Copy of this assignment with a completed table of values Calculations for the order of both filters Part a) Transfer functions for both filters Part b) Calculations of frequency responses for both filters Part c) Bode plots from Matlab for both filters Part d) Time responses from Matlab for both filters Part d) Calculations of filter circuit elements Part e) Schematic of filter circuit from PSpice Part e) Bode plots from PSpice Part e) Time response from PSpice Part e) Photo of circuit construction Part f) Table of frequency response data from testing circuit Part f) Bode plots from test data Part f) Time response from testing circuit Part f) Estimate of cost of 1000 circuits Part g)