ECG AmplifierBy:

Chenchen QiDouglas CihaJohn Hogan

ConsiderationsPreamplifier

Filter

Driven Right Leg Circuit

Preamp SpecsVoltage range: 1.9 - 3.8 V

Middle voltage: 2.85 V0.95V from center to each saturation point

Input signals:DC offset voltage range: ±0.3 VRange of linear operations of input: ±5 mV

Allowed Gain:0.95/0.305 V = 3.115

Preamp Circuit

G = 1 + 49.4k/RG

Choose RG = 25 kΩG = 3

Figure 1. LT1167 pin diagram [1]

FilterObserved ECG frequencies:

Clinical Bandwidth: 0.05 – 100HzMonitoring Bandwidth: 0.5 – 50Hz

Used 0.5 – 50Hz bandwidthAll that is needed to construct a monitorNaturally avoids 60Hz signal noise

Passive Band-pass Filter

We want fc,1 = 0.5 Hz and fc,2 = 50 Hzf0 = 1/ (2πRC)

Choose R1 = R2 = 1 MΩC1 = 3.18 nF C2 = 318 nF

Figure 2. Band-pass fitter [2]

Driven Right Leg Circuit

Figure 3. Driven right leg circuit [3]

Driven Right Leg CircuitPatient not connected to ground

Right leg connected to auxiliary amp output

Connected through a buffer and two, 50kΩ resisters, for patient safety

Figure 4. Right Leg Lead [4]

50kΩ 50kΩ

References[1]https://ay14-15.moodle.wisc.edu/prod/pluginfi

le.php/75950/mod_resource/content/1/LT1167%20instr%20amp.pdf

[2]http://www.electronics-tutorials.ws/filter/filter_4.html

[3]15.moodle.wisc.edu/prod/pluginfile.php/72917/mod_resource/content/1/BME%20DSP%20textbook.pdf

[4]https://ay14-15.moodle.wisc.edu/prod/pluginfile.php/76349/mod_resource/content/1/DRL-TexasInst-2011.pdf

Questions?