Design of a 3~5 GHz LNA with the Function of Both a Single-end Input and Differential Output is Achieved

In this paper, a fully integrated ultra-wideband (UWB) low noise amplifier (LNA) employing a cascode topology is designed with 0.18 μm RF CMOS technology. By using Matlab mathematical modeling of noise figure,the noise figure is optimized. By using a special architecture, the function of both a single-end input and differential output is achieved. The wideband input impedance matching is conducted by employing an RC feedback network, a degenerating inductor. The simulation results show that the average power gain (S21 or S31) is about 16.1 dB and the input return loss (S11) is less than -10.9 dB over the whole frequency range of 3 to 5 GHz. In addition, the noise figure (NF) is from 2.04 to 2.68 dB,the max phase error of output port is 4°, while consuming 18.4 mW under a 1.8 V single supply voltage.