Current mirror design for a Low Noise Amplifier

[aleemarp]

I am facing problem while designing a basic inductive source degeneration LNA. I fixed the gate bias of LNA for a particular current and got a noise figure of around 1dB. But when i used a basic current mirror(for the getting the same gate bias) the noise figure is increasing to the range of around 6dB. Can anyone give me clarifications for this increase?

 

[BigBoss]

Because you current source is noisy and it impacts the overall Noise Figure of the amplifier.There are some filtering techniques to decrease this effect coming from the current source.

 

[aleemarp]

Can you suggest how to filter out the noise from current source?

 

[Dominik Przyborowski]

You have to decrese current source transconductance. The simplest way is to increase it length, but it could deteriorate your frequency response. the second easy technique is to apply a degeneration.

There are also other techniques, but more sophisticated...