Design consideration for LPF with gain boosting in GHz-range applications

A 0.18 mum CMOS fifth order Butterworth low-pass filter with 24 dB programmable gain boost at its 1.2 GHz cut-off frequency for HDD applications is presented. A new G
_m
-LC architecture is proposed using feedforward path techniques to achieve the required boost. The gain of the feedforward path can be controlled to provide the variable boost. Simulation results shows that a 28/46 mA is drawn from a 1.8 V supply in the no-boost/max-boost cases respectively. Group delay variations for different boost values are limited to 10% from the no-boost case. At the nominal output voltage swing of 250 mVpp at 1.2 GHz, a THD of -42 dB is obtained