Low-voltage pseudo-differential transconductor with improved tunability-linearity trade-off

A new low-voltage pseudo-differential CMOS transconductor using transistors in the saturation region is presented. It keeps the input common-mode voltage constant, while its transconductance is easily tunable through a DC voltage preserving linearity for a moderate range of G_m values. Post-layout results for a 2.7 V-0.5 μm CMOS design dissipating less than 1.5 mW show a 1:2 G_m tuning range with an almost constant bandwidth over 600 MHz. Total harmonic distortion figures are below -60 dB over the whole range at 10 MHz up to a 100 μA_p-p differential output.