A self-biased transconductor with widely input linear range for Gm-C filters

Abstract

ABSTRACTIn this paper, a gain-boosting transconductor with widely input linear range and tunable control voltage is presented. A novel self-biased topology is employed in the negative feedback path of the gain-boosting structure to improve the linearity of the proposed transconductor. In fact, this self-biased topology results in a linear change for the drain voltage of the input drivers under the variation of the control voltage, while the input drivers operate in the triode region. In order to confirm the improved performance of the proposed transconductor, it is employed in a third order Butterworth low pass Gm-C filter. Therefore, the self-biased topology allows having more control on the cutoff frequency of the Gm-C filter. The proposed transconductor is designed and simulated in a 0.18 µm CMOS technology under a 1.8 V power supply. The small signal transconductance of the proposed circuit can change from 2.5 to 104.3 µA/V by tuning the control voltage. In addition, simulation results of the mentioned filter also show that the cutoff frequency properly changes between 500 KHz and 20.6 MHz, while third-order intercept point (IIP3) for this filter is between 7.55 and 21.4 dBm for different applications.