A Versatile Low-voltage CMOS Pseudo-Differential Transconductor with Improved Linearity

In this paper a pseudo-differential continuous-time CMOS transconductor suitable for applications in low-voltage systems over the high frequency range is presented. The basis is to split each transistor in the classical fully balanced grounded pair into two matched transistors that form differential pairs. This makes possible to maintain constant the input common mode voltage, keeping it independently of the continuous transconductance adjustment. Results for a 0.5 μm CMOS design show a moderate G_m tunability range with an almost constant bandwidth over 400 MHz, while total harmonic distortion figures are kept below -60 dB over the whole gain range at 10 MHz up to a 100 μA_p-p differential output. The proposed transconductor, compatible with purely digital processes, is very compact in terms of silicon area and consumes less than 1.5mW from a single 2.7V supply.