Active-Gm-RC Continuous-Time Biquadratic Cells

Abstract

An analog CMOS low-pass Active-Gm-RC biquadratic cell is presented. The cell combines the advantage of GM-C filters (no parasitic poles) with the advantages of Active-RC filter (large linear range). Two additional digital-based circuits allow to control the pole frequency and to reduce the effects of the non-dominant poles. A 4th order low-pass Butterworth filter with a 2.11 MHz cut-off frequency and a DC-gain of 32 dB for UMTS receiver has been designed in a 0.18 µm CMOS technology with 1.8 V supply voltage. The filter exhibits a-93 dBV input-referred noise with a power consumption of 2.16 mW while the linearity performances corresponds to an in-band IIP3 of 4 dBm and an out-of-band IIP3 of 35 dBm. An Active Gm-RC band-pass cell is presented as possible alternative application.