Low-Voltage Tunable Pseudo-Differential Transconductor with High Linearity

A novel tunable transconductor is presented. Input transistors operate in the triode region to achieve programmable voltage-to-current conversion. These transistors are kept in the triode region by a novel negative feedback loop which features simplicity, low voltage requirements, and high output resistance. A linearity analysis is carried out which demonstrates how the proposed transconductance tuning scheme leads to high linearity in a wide transconductance range. Measurement results for a 0.5 mu m CMOS implementation of the transconductor show a transconductance tuning range of more than a decade (15 mu A/N to 165 mu A/V) and a total harmonic distortion of -67 dB at 1 MHz for an input of 1 V-pp and a supply voltage of 1.8 V.