Figure 5. Low-pass filter-EKG Through Sound-Card
The low-pass filter, presented in figure 5, allows signals with frequencies up to 34 Hz (cutoff
frequency) to pass unaltered while it strongly attenuates those with frequencies exceeding the
cut-off frequency. It is an active filter, of the butterworth sallen-key type which contains one of the
four operational amplifiers of the TL084 integrated circuit.