A second-order low power current-mode continuous-time sigma-delta modulator

A fully differential second-order continuous-time sigma-delta modulator based on the nonlinear transconductance-capacitor (G_m-C) is presented. The nonlinear transconductance is designed based on current-mode technique and it uses MOS transistors operating in subthreshold region. The proposed converter that designed in 0.35 um CMOS process features low power consumption (<80uW), low supply voltage (1V) and 55 db dynamic range. Simulation results by HSPICE confirm the validity of the proposed technique.