1. By: Chenchen Qi Douglas Ciha John Hogan
ECG Amplifier
By:
Chenchen Qi
Douglas Ciha
John Hogan

2. Considerations
Preamplifier
Filter
Driven Right Leg Circuit

3. Preamp Specs Voltage range: 1.9 - 3.8 V Input signals: Allowed Gain:
Middle voltage: 2.85 V
0.95V from center to each saturation point
Input signals:
DC offset voltage range: ±0.3 V
Range of linear operations of input: ±5 mV
Allowed Gain:
0.95/0.305 V = 3.115

4. Preamp Circuit G = 1 + 49.4k/RG Choose RG = 25 kΩ G = 3
Figure 1. LT1167 pin diagram [1]

5. Filter Observed ECG frequencies: Used 0.5 – 50Hz bandwidth
Clinical Bandwidth: 0.05 – 100Hz
Monitoring Bandwidth: 0.5 – 50Hz
Used 0.5 – 50Hz bandwidth
All that is needed to construct a monitor
Naturally avoids 60Hz signal noise

6. Passive Band-pass Filter
Figure 2. Band-pass fitter [2]
We want fc,1 = 0.5 Hz and fc,2 = 50 Hz
f0 = 1/ (2πRC)
Choose R1 = R2 = 1 MΩ
C1 = 3.18 nF
C2 = 318 nF

7. Driven Right Leg Circuit
Figure 3. Driven right leg circuit [3]

8. Driven Right Leg Circuit
Patient not connected to ground
Right leg connected to auxiliary amp output
Connected through a buffer and two, 50kΩ resisters, for patient safety
50kΩ
50kΩ
Figure 4. Right Leg Lead [4]

9. References
[1] 15.moodle.wisc.edu/prod/pluginfile.php/75950/mod_res ource/content/1/LT1167%20instr%20amp.pdf
[2]
[3]15.moodle.wisc.edu/prod/pluginfile.php/72917/mod_r esource/content/1/BME%20DSP%20textbook.pdf
[4] 15.moodle.wisc.edu/prod/pluginfile.php/76349/mod_res ource/content/1/DRL-TexasInst-2011.pdf

10. Questions?