A 0.6-V Power-Efficient Active-RC Analog Low-Pass Filter With Cutoff Frequency Selection

This article presents a fully differential (FD) low-voltage (LV) fourth-order Butterworth active-RC low-pass filter (LPF) with a maximum cutoff frequency (f(0)) of 160 MHz, f(0) programmability, and adaptive power. The proposed filter targets communication systems requiring high and reconfigurable f(0) at supply voltages (V(DD)s) of 0.6 V. The filter is implemented with an active-RC topology, a programmable f(0) between four steps, 20/40/80/160 MHz, and a f(0) fine-tuning option after fabrication via capacitor banks. A compact LV FD amplifier with feedforward gain-boosting implementation is used to meet the stringent filter's performance. The novel amplifier achieves an open loop gain of 66 dB and a maximum unity-gain frequency (UGF) of 759 MHz with V-DD = 0.6 V and 5.27 mW of power dissipation. Using the proposed amplifier, the filter achieves the highest f(0) reported in the literature for LV active-RC implementations and 40% power reduction over similar high-f(0) LV filters. The filter was fabricated in a CMOS 130-nm technology; it has a THD = 50.7 dB, signal-to-noise and distortion (SNDR) = 45.37 dB, P-1dB = 4.26 dBm and 520-mu V RMS integrated noise over the filter's bandwidth (BW), while consuming 23.8 mA from a 0.6-V supply for f(0) = 160 MHz.