A low-voltage and low-power gm-C low-pass filter with tunable cut-off frequency suitable for a wide range of biomedical applications

Abstract

This paper presents a low-pass Butterworth gm–C filter with a widely tunable cut-off frequency suitable for biomedical applications. The filter’s main building block, the operational transconductance amplifier (OTA) with a new tunable tail current sources generation circuit, provides a wide transconductance tuning range using a voltage supply to support the specifications of various biomedical applications. Moreover, this paper employs a source-degeneration technique to enhance the linearity of the OTA, which can deteriorate under low supply voltage conditions. The circuits are designed in a 0.18 μm CMOS process with a 1.2 V supply voltage. The filter has 302 nW power consumption, 47 Hz to 333 Hz tunable cut-off frequency, 313 μV_rms to 90 μV_rms input-referred noise voltage, and a dynamic range of 56.17 dB to 71.15 dB in the cut-off frequency tuning range. Besides, the paper uses process corners and temperature variations simulation to verify the efficiency of the filter after fabrication. The resulting specifications confirm the filter’s suitability for EEG, EMG, ECG, EOG, ERG, IEGM, and ENG biomedical applications.