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

Abstract

This article presents a fully differential (FD) low-voltage (LV) fourth-order Butterworth active- RC low-pass filter (LPF) with a maximum cutoff frequency $(f_{o})$ of 160 MHz, $f_{o}$ programmability, and adaptive power. The proposed filter targets communication systems requiring high and reconfigurable $f_{o}$ at supply voltages $(V_{\mathrm {DD}}s)$ of 0.6 V. The filter is implemented with an active- RC topology, a programmable $f_{o}$ between four steps, 20/40/80/160 MHz, and a $f_{o}$ 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 $V_{\mathrm {DD}} = 0.6$ V and 5.27 mW of power dissipation. Using the proposed amplifier, the filter achieves the highest $f_{o}$ reported in the literature for LV active- RC implementations and 40% power reduction over similar high- $f_{o}$ 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, $P_{\mathrm {1dB}} = 4.26$ dBm and 520- $\mu \text{V}$ RMS integrated noise over the filter’s bandwidth (BW), while consuming 23.8 mA from a 0.6-V supply for $f_{o} = 160$ MHz.