balun balanced side impedance choice

Balanced side impdedance usually choose 50Ω or 100Ω. It seems 100Ω is better for it will decrease the LNA NF. However, any bad side it will bring? thanks

i think it will depend on the impedance of the next stage

most of the BALUN i saw was 50 to 100 or 50 to 200 Ohms

khouly

NF will be better as you expect to have a virtual noiseless voltage gain in front of your LNA due to the impedance ratio of the Balun. For the same reason you will have a decreased linearity of the amplifier.
I hope it can help.
Mazz