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
_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
_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
_DD
= 0.6 V and 5.27 mW of power dissipation. Using the proposed amplifier, the filter achieves the highest fo 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
_1dB
= 4.26 dBm and 520-μV 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.