BRAIN Journa-EKG Through Sound-Card-Figure 5. Low-pass filter

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