vfone said:In a cascode topology the noise introduced by the cascode device (upper transistor added to improve stability of the amplifier) it will be additional to the initial noise.
So, a cascode always will get higher noise figure than a single device (or at least very close).
The pHEMT ATF-38143 from Avago has one of the lowest NF on the commercial market, but has higher NF than you are looking for.
Abhishekabs said:For 0.25dB NF NEC transistors are good, but at this frequency & 0.2dB NF it is hard. you may need to make superconducting LNA
Added after 51 seconds:
I mean you need to use cooling techniques.
stevie-g said:Ya... I know it's a bit tough.
I thought there got any new topology I don't know.
Anyway, thanks man!