tony Sir,
For designing the LNA ( frequency range 1 GHz to 1.5GHz), I used drain resistance Rd= 135 ohm, source resistance Rs= 2 ohm, resistance between drain and source Rds= 2000 ohm . I set Vds =1.78v, Id= 24.1mA, Vgs = -0.2V , L= 8nH. I got the NF =0.26596 S(2,1) = 7.1786 at 1.3 GHz. I achieved NF and Gain without connecting feed back resistor between gate and drain . When I connected the feedback resistance between gate and drain R=340 ohm, I am getting the NF more and Gain very less NF=1.2314dB, Gain= 3.4314. What I have to do for getting NF lessthan 0.3 dB and Gain more than 7 mag with achieving the stability. If I don't connect the resistance , was getting NF less than 0.3 dB and Gain more 7 mag without achieving stability, but once I connect the feedback resistance between drain and gate Rdg=340, achieve the stabilty , but loosing NF and Gain. Can u help me , How to get out from this problem. I used the transistor NEC3508 nonlinear .