Low-voltage linearly tunable CMOS transconductor with common-mode feedforward

This paper presents a new low-voltage pseudo-differential continuous-time CMOS transconductor for wideband applications. The proposed cell is based on a feedforward cancellation of the input common-mode signal and keeps the input common mode voltage constant, while the transconductance is easily tunable through a continuous bias voltage. Linearity is preserved during the tuning process for a moderate range of transconductance values. Simulation results for a 0.35 mu m CMOS design 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 200 mu A(p-p) differential output. The proposed cell consumes less than 1.2 mW from a single 2.0 V supply.