Low-Power Architecture and Circuit Techniques for High-Boost Wide-Band $G_m$–$C$ Filters

A 330-MHz fifth-order G
_m
-C continuous-time low-pass filter with 24-dB boost is presented. Existing solutions are found to be unsuitable for low-power, wide-band, and high-boost operation. The proposed solution realizes two symmetric real axis zeros by efficiently combining transfer functions associated with all nodes of cascaded biquad cells. Application of Gilbert cell as a variable transconductor, for achieving constant parasitic capacitance across wide programmability range, is illustrated. A new common-mode feedback error amplifier that improves common-mode accuracy without compromising on bandwidth or circuit complexity is introduced. A prototype is fabricated in a standard 0.35-mum CMOS process. Experimental results show -41 dB of IM3 for 250-mV peak-peak swing with 43 mW of power dissipation