A 50–300-MHz Highly Linear and Low-Noise CMOS $Gm{hbox{-}}C$ Filter Adopting Multiple Gated Transistors for Digital TV Tuner ICs

In this paper, a highly linear and low noise CMOS active tracking low-pass filter is presented to overcome a local oscillator harmonic mixing problem for Advanced Television Systems Committee terrestrial and cable digital TV tuner integrated circuits. A transconductor linearization technique based on a method of multiple gated transistors is adopted to improve the linearity performance. The cutoff frequency of the proposed filter is tunable from 50 to 300 MHz. Fabricated in a 0.18-$mu{hbox{m}}$ CMOS process, the filter provides a minimum input referred noise density of 5 $ {hbox{nV}}/sqrt{hbox{Hz}}$ and maximum in-band output referred third-order intercept point of 16.9 dBm, while drawing an average current of 40 mA from 1.8 V. The total chip area is 1 mm $times$ 0.9 mm.