A High-Linear Low-voltage CMOS Tunable Transconductor for VHF Filtering

In this paper a new low-voltage pseudo-differential continuous-time CMOS transconductor is presented for applications in the video frequency range. By splitting each transistor in the classical fully balanced grounded pair into two matched transistors that form differential pairs, it is possible to keep 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. Post-layout results from a 0.5 mum CMOS integrator design show a 37 to 74 MHz tuning range for 1 pF load capacitors with an excess phase <0.5deg and a dynamic range better than 57.8 dB for a 0.1% THD over the whole tuning range. The proposed cell consumes less than 1.5 mW from a single 2.7 V supply.