A design solution for bulk-driven tunable transconductor capable of working under extremely low supply/consumption with rail-to-rail input common-mode range is presented in this work. The proposed transconductor topology consists of six bulk-driven CMOS inverters, and it uses a very simple biasing circuit for the transconductance tuning. The design robustness was verified for 0.5 and 0.25 V power supplies offering the advantages of the current-controlled input transconductance. For 0.5 V power supply, the proposed transconductor has 0.075-10.2 transconductance tuning range, input-referred intercept point IP3 = 1.81 V, and 4.62 MHz bandwidth for 3 current consumption. The design robustness of the tunable transconductor was verified by means of computer simulation using triple-well 0.18 CMOS process.