A tunable CMOS transconductor for ultra-low Gm with wide differential input voltage range

A differential input, single ended output transconductor with gm in the range 0.5-5 nS is presented. The circuit uses a source coupled pair operated in triode region. The need of providing a fixed common mode input voltage, which afflicts circuits based on the same principle, is removed by adopting an original topology. The results of simulations based on the 0.35 ?m BCD6 process of STMicroelectronics are presented.