spbhu
Member level 2

Hi, I have built my LNA circuit, the transistor I used is 40/0.18um, the biasing current is 0.5mA. And Vgs=535mV, from the simulation result, I found nf(2)=~3.4~3.6dB, while NFmin is about 2~2.5dB. The resonant frequency is 2.5GHz. Can I adjust the circuit to make nf(2) approach NFmin? How to change the circuit, can anyone help me?
Another problem is that, since the low current consumption requirement, the biasing gate voltage is quite low, and Vod<100mv, does it matter? Since it is already in moderate region? What could be the problem for low Vod?
Many thanks.
Added after 2 hours 6 minutes:
Some additions:
The topology I used is CS inductive degeneration. The result from my simulation shown that, the resonant of NFmin at 0.8GHz, while the nf(2) of gain and s11 resonate at 2.5GHz, what is the reason? Does it mean nf(2) consider the parasitic resistance of the inductor Lg and Ls, while NFmin donot? Thanks
Another problem is that, since the low current consumption requirement, the biasing gate voltage is quite low, and Vod<100mv, does it matter? Since it is already in moderate region? What could be the problem for low Vod?
Many thanks.
Added after 2 hours 6 minutes:
Some additions:
The topology I used is CS inductive degeneration. The result from my simulation shown that, the resonant of NFmin at 0.8GHz, while the nf(2) of gain and s11 resonate at 2.5GHz, what is the reason? Does it mean nf(2) consider the parasitic resistance of the inductor Lg and Ls, while NFmin donot? Thanks