EE 470 - Biomedical Signals and Systems - Exp. 6

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Experiment No. 6 ( Project #2 )

TWIN - T / LEAD-LAG NETWORKS OBJECTIVE: To refresh the student’s knowledge on the important fundamental topic of frequency response using more complicated circuits than the simple RC circuits.

Some fundamental characteristics of test equipment involved in test and measurement will be studied. Accuracy and precision of the measurement and resultant uncertainty in the data will be analyzed. Frequency responses of lead-lag and twin-T networks will be ascertained.

CIRCUITS:

The Twin – T Circuit

The Lead / Lag Circuit

10nF

10k

Vin Vout

RL

10nF

20nF

10k

5k

C1=33 nF

R1=33k

R2=10k C2

Vin Vout

C2=10 nF

EE 470 - Biomedical Signals and Systems - Exp. 6

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EXPERIMENTAL PROCEDURE:

a) Construct the lead-lag network shown in the figure. Apply a sine

wave of 4 volts peak-to-peak amplitude and by changing its frequency decide on the cut off frequencies.

b) Identify about 15 frequencies that are critical for you to estimate

the frequency response of the circuit. Determine the amplitude and phase responses at those frequencies.

c) Interchange R1C1 with R2C2 and repeat 1 and 2.

d) Construct the twin-T network shown in the figure. Repeat steps 1

and 2 and obtain the frequency response characteristic carefully.

Results and Discussions:

1. Record all measurements you have made into an EXCEL spreadsheet.

2. Plot amplitude and phase responses using linear scales and log scales. Also plot the Bode plots.

3. Calculate the time constants and cut off frequencies for the networks you have used.

4. Discuss the results you have obtained in the class as an active learning exercise

5. Use the results to solve the design in active learning exercises in pages: 12 – 18 in part-D, system description.