Low-voltage CMOS GM-C filter with rail-to-rail common-mode voltage

In this paper, a CMOS design of low-voltage 5th-order elliptic low-pass GM-C filter with rail-to-rail common-mode input voltage is introduced. The Operational Transconductance Amplifier (OTA) inside this filter is a low-voltage rail-to-rail voltage-to-current converter (V-I converter). In this V-I converter, an N-type V-I converter cell is connected in parallel with its counterpart, a P-type V-I converter cell, to achieve common-mode rail-to-rail operation. Maximum-current selecting circuits are utilized to generate constant-gm output currents for this OTA. This 5th-order elliptic low-pass GM-C filter operates at a supply voltage of 3 V and has a cutoff frequency of 500 kHz.