The LNA stability checked through phase margin and k factor

[chunlee]

As i know, we can check the stability of the LNA through phase margin and k factor (which can calculated from s-parameter).

is it the stability that calculated by phase margin and k factor is means for the same type of stability? or they mean different types of stability?

Thank you for your help...

 

[springf2000]

Re: LNA stability

when i do the LNA and check the stabiltiy, i use the ADS to do this job automatically

 

[flatulent]

Re: LNA stability

Phase margin is more for feedback systems. The stability of an RF amplifier is usually drawn on a smith chart showing input and output terminations that cause or not oscillations. This is done for a wide range of frequencies, not just the one you are to use. Then you examine (or design) the input and output networks to be in the stable impedance range for each frequency.

 

[mmarwan]

Re: LNA stability

for springf2000, how do u automatically check the stability of the LNA using @ds.
i designed an LNA and i doubt that it oscillates at 2 GHz, how can i be sure of that?!
THANKS IN ADVANCE.

 

[khouly]

Re: LNA stability

simply check the real value of the zin and zout of the amp

to prevent any oscillation
Re(Zs) > |Re(Zin)|
this make sure that the amplifier will not oscillate in input port
Re(Zl) > |Re(Zouy)|

and check gonzalez book for details

and u can do this very easly in @DS

wish this help

khouly

 

[countmybones]

Re: LNA stability

You can use the built in funtion in ADS, in S-parameter simulation. Like s_stab_circle, mu etc...