Design Of Broadband Low Noise Amplifier

Broadband Low Noise Amplifier(LNA)is the first active circuit module for multistandard and multi-band RF receiver circuit system.The performances such as gain,noise and linearity directly affect the performance of the RF receiver.However,the performance of input matching,gain,noise and bandwidth in broadband low noise amplifier are constrained by each other.For example,due to the constraints of the input matching condition,the feedback resistor of broadband composite structure resistive feedback common source(CS)LNA circuit structure can only be selected in a certain range,so that the noise figure of the circuit can not be further reduced.To solve this problem,two improved structures are proposed in this paper.PMOS transistors cross-connected from the output to the input are added to the broadband composite structure resistive feedback CS-LNA.A new active negative feedback branch is introduced to constructe the broadband composite structure resistive feedback and negative feedback CS-LNA architecture.By adjusting the transconductance of the added PMOS transistor,this architecture increases the freedom of input matching and solves the problem that the original composite structure resistive feedback CS-LNA's feedback resistance is limited by input matching,which could increase the resistance of the feedback resistor while the input matching is maintained,improve the contradiction between noise,input matching,gain and bandwidth of the LNA,reduce the noise figure and improve the voltage gain of the LNA.Changing the method of broadband composite structure resistive feedback CS-LNA that uses the feedback resistor to satisfy input matching,and the broadband composite structure active feedback CS-LNA architecture is constructed by adding active negative feedback structures that NMOS transistors are connected from the output to the input.Compared to the resistive feedback,the active feedback has a higher degree of freedom to satisfy the input matching.Since the composite structure active feedback CS-LNA has no feedback resistor to limit the output impedance and generate noise,higher gain and lower noise figure can be achieved in the LNA design.The broadband composite structure resistive feedback and negative feedback CS-LNA is designed by using TSMC 180 nm CMOS technology,and the simulation results show that the power gain is improved by 3.5dB and the noise figure is reduced by 0.38 dB compared with the composite structure resistive feedback CS-LNA in the frequency range of 0.05~1.5GHz.The broadband composite structure active feedback CS-LNA is designed by using UMC 90 nm CMOS technology.The simulation results show that the power gain is improved by 3.7dB and noise figure is reduced by 0.44 dB compared with the composite structure resistive feedback CS-LNA in the frequency range of 0.03~3GHz.