An eighth-order CMOS low-pass filter with 30-120 MHz tuning range and programmable boost

A CMOS low-pass filter with programmable boost is presented. The architecture is a G/sub m//C type with the G/sub m/ value controlled through a resistor servo approach. The transfer function has been optimized in order to reduce the sensitivity to component parameter variations. The 1:4 tuning range is achieved by exploiting a dual-loop control over a degenerated differential pair. At the nominal output voltage swing of 200 mV/sub pp/ differential, a THD better than 40 dB is guaranteed. The high-frequency boost is programmable between 6 and 14 dB. This filter, realized as a cascade of biquad and first-order cells, is implemented in a 0.25-/spl mu/m 2.5-V CMOS technology. It dissipates 120 mW with f/sub c/=120 MHz and has a die area of 0.23 mm/sup 2/.