Low-voltage, micropower weak-inversion CMOS GM-C filter

In this paper, a CMOS implementation of a low-voltage, micropower 5th-order elliptic low-pass GM-C filter is presented. The Operational Transconductance Amplifier (OTA) in this GM-C filter design is implemented by a low-voltage voltage-to-current converter (V-I converter) working in the weak-inversion region. The transconductance can be tuned by control DC currents or DC voltage. This V-I converter can be used as a basic building block to construct low-voltage, micropower analog VLSI signal processing systems. Also, the filter provides a practical means for implementing very large time constants on-chip allowing single-chip solutions at very low frequencies. This 5th-order elliptic low-pass GM-C filter operates at a supply voltage of 3 V and has a tunable cutoff frequency from 140 Hz to 3.5 kHz