Lab 1 Grading Sheet

ECE 445 Biomedical Instrumentation
Fall 2012
Lab 8 Prelab
The prelab is required in order to perform the lab. Complete this prelab before attending the lab and show the
completed materials to the TA at the beginning of your lab.
For Lab 8, we will be designing filters using a different opamp chip, the UA747. This chip contains two identical
UA741 opamps, allowing you to build a simple cascade bandpass filter with a single chip. A datasheet for the
UA741 is posted on the class website. To perform SPICE simulations for the UA741, you should use the
.subcircuit definition provided on the next page rather than the previous .subcircuit for the OP467. This
subcircuit is also posted on the website as a .txt file.
Following the steps below, use the examples and information provided in the background section of Lab 8 to
design your own low pass, high pass, and cascaded bandpass filters suitable for your Lab 6-7 instrumentation
amplifier. The bandpass filter will be connected as shown below and used in this lab to record ECG signals. You
should design for an input ECG signal with a maximum amplitude of about 30mV and information content in the
0.5 – 180Hz frequency range.
1. Considering your instrumentation amplifier has been designed to provide a gain of 30 V/V, determine what
gain your passband filter should provide so that they do not saturate the output when the input ECG signal
is at its maximum value. Assume the filters are connected to a 0-10V power supply and that your output
should remain within 1 – 9 V (because most amplifiers cannot function correctly all the way to the supply
voltage). Use the equation below to calculate filter gain.
max_output_swing = max_input_amplitude * amplifier_gain * filter_gain
Next, consider that the filter gain will be split between the low pass and high pass filters. Round the filter
gain down to an even integer value and assign ½ of this gain to low pass and ½ to high pass filter circuits.
Record your calculated (max) filter gain and the rounded gain values assigned to each of the two filter
circuits. Turn these in with your circuit sketch and SPICE plots below.
2. Using the low and high pass filter circuits shown in the Lab 8 Background, calculate all the R and C values
to provide the gain and bandwidth needed for recording ECG signals. Sketch a circuit diagram for both high
and low pass filters and label component values to match your hand calculations. Remember to choose
reasonable R and C values that can be implemented with components in the lab: R = {100Ω – 10MΩ}, C =
{1pF – 1µF}.
2. Implement your low and high pass filter designs in SPICE and test the frequency response to see if your
gain and cutoff frequencies are correct. Adjust your circuit as necessary to achieve desired performance.
Print the frequency response plots for the final low and high pass filters.
3. In SPICE, combine the low and high pass filters to form a cascade bandpass filter (see figure above). Test
the frequency response to see if your gain and cutoff frequencies are correct, and adjust your circuit as
necessary to achieve desired performance. Print the frequency response plot for the bandpass filter, adding
labels for passband gain and upper and lower -3dB frequencies.
4. In SPICE, combine the bandpass filter with your instrumentation amplifier from Lab 6 prelab, with the filter
following the output of the instrumentation amplifier. Note, you will have two different opamp models in your
SPICE netlist, but that should not be a problem. Simulate the frequency response and measure the
passband gain and upper and lower -3dB frequencies. Once everything is working correctly, print the
frequency response plot and label the measured characteristics.
ECE 445 Biomedical Instrumentation
* UA741 OPERATIONAL AMPLIFIER "MACROMODEL" SUBCIRCUIT
* CONNECTIONS: NON-INVERTING INPUT
*
| INVERTING INPUT
*
| | POSITIVE POWER SUPPLY
*
| | | NEGATIVE POWER SUPPLY
*
| | | | OUTPUT
*
|||||
.SUBCKT UA741 1 2 3 4 5
*
C1 11 12 4.664E-12
C2 6 7 20.00E-12
DC 5 53 DX
DE 54 5 DX
DLP 90 91 DX
DLN 92 90 DX
DP 4 3 DX
EGND 99 0 POLY(2) (3,0) (4,0) 0 .5 .5
FB 7 99 POLY(5) VB VC VE VLP VLN 0 10.61E6 -10E6 10E6 10E6 -10E6
GA 6 0 11 12 137.7E-6
GCM 0 6 10 99 2.574E-9
IEE 10 4 DC 10.16E-6
HLIM 90 0 VLIM 1K
Q1 11 2 13 QX
Q2 12 1 14 QX
R2 6 9 100.0E3
RC1 3 11 7.957E3
RC2 3 12 7.957E3
RE1 13 10 2.740E3
RE2 14 10 2.740E3
REE 10 99 19.69E6
RO1 8 5 150
RO2 7 99 150
RP 3 4 18.11E3
VB 9 0 DC 0
VC 3 53 DC 2.600
VE 54 4 DC 2.600
VLIM 7 8 DC 0
VLP 91 0 DC 25
VLN 0 92 DC 25
.MODEL DX D(IS=800.0E-18)
.MODEL QX NPN(IS=800.0E-18 BF=62.50)
.ENDS
Fall 2012
ECE 445 Biomedical Instrumentation
Fall 2012
Lab 8 Grading Sheet
PARTNER NAMES: ___________________________________________________________
Exercise 1
Low Pass Filter
Step 7
Output voltage: ___________, Gain (pass band):________, Frequency: __________
Step 8
Step 9
Output voltage @ -3dB: ___________, -3dB frequency: __________
Unity gain bandwidth: ___________
High Pass Filter
Step 10
Output voltage: ___________, Gain (pass band):________, Frequency: __________
Output voltage @ -3dB: ___________, -3dB frequency: __________
Unity gain bandwidth: ___________
Band Pass Filter
Step 11
Passband Gain:________, upper -3dB freq.: __________, lower -3dB freq.: __________
Bandwidth: ___________, Q-factor: ___________, Damping factor: ___________,
Exercise 1: TA Check off: _________________
Exercise 2
ECG Signal from Function Generator
LabVIEW Setup
Step 9
Exercise 2a: TA Check off: _________________
Step 12
Exercise 2b: TA Check off: _________________
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