Transistor stabilisation at low frequencies

[inass57]

Hello everyone,

I'm trying to design a LNA using the NXP transistor BFU730f, howerver i've been stuck for days trying to stabilize it at low frequencies. i've tried the basic stabilizing circuits, while i was able to stabilize it with some, it either incresed the NFmin or decreased the max gain.

The specification for my LNA are NF=1.5 and G=13dB so i need the NFmin to be at least 1.2 and Gmax=14.
the frequency of interest is 9.35GHz but i need the transistor to be inconditionally stable.

Can u please suggest anything else i can try.

Thank you in advance.

 

[BigBoss]

Plot the Input and Output Stability Circles and place some resistances either at Input or Output ( maybe both ) to push out the circles out of Smith Chart.
Applying a series/parallel feedback may be a solution.There are many options to push out these circles, play around and find yourself.

 

[biff44]

C4 is way too small. AND you have no bypass capacitor across the 4V supply, like where you should have a 1000 pf in parallel with a .1 uf