Design of 900∼2250MHz broad-band differential LNA with variable gain

摘要

A broad-band variable-gain differential LNA for Satellite-broadcast TV operating in the frequency bands of 900MHz∼2250MHz is presented. A third-order Chebyshev band-pass Filter is used as input matching circuit; Two cascode-structure circuits are employed as the key stage of gain (KSG) and the control stage of gain (CSG) respectively, both of the output loads of the two-stage circuits adopt shunt-peaking structure, the CSG change the value of the gain with making use of the drain-to-source Resistance Miller effect and feedback of transistors; A source-follower is designed to match output. In the TSMC 0.18μm CMOS technology, 1.8V operating voltage and 1.3V∼1.6V control voltage of gain, this LNA achieve 75Ω input and output matching and broad variable-gain ranges, moreover, acquire excellent noise performance, linearity and low power consumption.