A New Technique to Implement Ultra-low Frequency Analog Filters for Electrophysiological Signal Acquisitions

This paper describes a new method to implement ultra-low frequency analog filters for electrophysiological signal acquisitions. Unlike the traditional pseudo-resistor or trans conductor-capacitor architectures, the proposed continues time filters employed current steering integrators which help decrease the capacitor area and reducing the total harmonic distorting (THD) simultaneously. Three basic structures (high pass, notch and low pass filters) were designed by proposing this technique and were implemented by 0.18 μm CMOS technology. Measurement results showed that the-3 dB of the low pass and high pass filters were 220 Hz and 0.05 Hz and notch frequency center of notch filter 50 Hz. Besides, the three filters´ THD were measured to be-76 dB, -76 dB and -80 dB which are the lowest values with the comparison with other state-of-the-arts.