A 2.3mA 240-to-500MHz 6th-order active-RC low-pass filter for ultra-wideband transceiver

This paper presents a 6^th-order active-RC low-pass filter with 240 MHz to 500 MHz tunable bandwidth, which is suitable for the ultra-wideband transceivers. The filter consumes only 2.3 mA from 1.8 V supply voltage, which is mainly attributed to the proposed highly power-efficient operational amplifier (Opamp) with an adaptive-biased pole-cancellation push-pull source follower as the buffer stage to drastically extend the bandwidth. The technique of high-frequency common-mode rejection using parasitic capacitor is utilized to guarantee the Opamp stability. In addition, the filter adopts the Q-tuning technique and Opamp GBW compensation mechanism, which relax the GBW requirement of the Opamp to further reduce the power consumption. The filter achieves 1.36 pW/pole/Hz normalized power, 13.1 nVA√Hz input-referred noise density, 15.9 dBm in-band IIP3, and 34 dBm out-of-band IIP3, respectively. The chip is fabricated in a standard 0.18 μm CMOS process, and occupies 0.23 mm² silicon area without pads.