Improvements in Electrocardiography Smoothening and Amplification

The electrocardiogram (ECG or EKG) is a graphic recording of the time-variant voltages produced by the myocardium during the cardiac cycle. The P, QRS, and T waves reflect the rhythmic electrical depolarization and re-polarization of the myocardium associated with the contractions of the atria and ventricles. The electrocardiogram is generally used clinically in diagnosing diseases of the heart. Hence, it must be very accurate. The ECG waveform is a periodic signal with bandwidth of 0.05 Hz to 100 Hz. Amplitude is typically 1 milli-volt peak to peak in the presence of much larger (1000 times larger) external high frequency noise plus 50/60 Hz interference common mode voltages (common to all electrode signals). We present a method to eliminate much of the noise using a pre-amplifier design with high common mode rejection ratio and high input impedance. We verify our results using computer simulation of the signal via the software MULTISIM 9.0.