Highly linear, tunable, pseudo differential transconductor circuit for the design of Gm-C filters

This paper describes the circuit level implementation of a transconductor cell that is intended to be used in open loop configuration for the design of Gm-C filters in CMOS technology. The circuit uses a fixed transconductor cascaded with a variable gain stage. The fixed transconductor is highly linear for a wide input signal swing that is close to the rails. The variable gain stage is constructed using a current mode translinear circuit. The cell is tunable to enable compensation for process, temperature, and voltage variations and to enable the adjustment of the overall filter´s characteristics. The transconductor cell was designed in 0.35 μm TSMC CMOS technology and it is intended to operate from a 2 V supply. The physical design was carried out for several cells with different transconductance. The test chip has been fabricated and it is currently under testing.