A 40 to 900 MHz CMOS broadband differential LNA for A DTV RF tuner

This article describes a 40 to 900 MHz CMOS broadband differential LNA with gain control for a DTV RF tuner application. The LNA is fabricated in a TSMC 0.18 μm CMOS process. The broadband differential LNA uses dual-feedback and shunt-shunt feedback topologies to achieve high gain and a flat broadband response. The LNA is designed with 75 Ω differential input and output impedances for a 75 Ω TV system application. The circuit measurement is performed using an FR-4 PCS test fixture. In the frequency range from 40 to 900 MHz, the LNA exhibits a gain of 20.26±0.41 dB, a noise figure less than 5 dB, and an input P1dB between -19.5 and -20.3 dBm. The gain tuning range is from 20 to -42.8 ±4.9 dB over the 40 to 900 MHz range. The power consumption is 43 mW at V _DD=18V.