A Low-Voltage, High Linear Programmable Triode Transconductor

This paper presents a new tunable pseudo-differential transconductor topology. A compact feedback loop able to operate with low supply voltage is employed that holds the input transistors in triode region and provides high output resistance. This control loop allows keeping high linearity in a wide range of transconductance. The circuit has been fabricated in a 0.5 mu m CMOS technology with a power supply of 1.8 V. The transconductance gain is tunable from 15 to 165 mu A/V with a measured total harmonic distortion of -67 dB at 1 MHz for an input voltage of 1 Vpp. The circuit maintains the linearity at higher frequencies with a third-order intermodulation below -55 dB at 10 MHz.