Balanced OTA-C Elliptic Cauer Filters for Biomedical Applications

This work presents a new circuit design for higher order elliptic Cauer filters. The proposed active realization is based on OTA-C structure, employing differential input balanced output operational transconductance amplifiers (OTAs) and grounded capacitors. Third, fourth, and fifth order lowpass Cauer filters are presented. The terminals of the OTAs are efficiently used during the circuit implementation of the the filters, providing minimum possible number of components. The proposed filter response normalized at notch frequency can be used for filtering out undesired noise signals accompanying acquired biopotential signals. The proposed elliptic Cauer low pass filters (LPF) can replace both LPF and notch filter used in biopotential signal detection system. A modified fourth-order filter with a single notch at 50/60 Hz to eliminate the power-line interference signal is simulated and compared to the modeled response. The notch frequency can be controlled by the terms present in the numerator of the transfer function.