i m making an LNA with s-parameters values as follows at 2.4Ghz:
1)s11 = 0.775 ang(-68.1)
2)s12 = 0.079 ang(54.5)
3 s21 = 5.602 ang(117.4)
4)s22 = 0.437 ang(-42.3)
and i want to stablize the transistor by a resistive load in output.but i m not able to find suitable resistive load which can stabilize this transistor .please help me in this regard.....
thanks for the help dude...but how did you get these values?
man if u have any refence or material please send it 2 me....my mail id is saiyan4aks@gmail.com
To stabilize it just put a low value resistor in shunt to the s2p file. How ever you will loose the gain, NF and RL etc.
So it is better to do the design using good simulator.
You need to plot the NF circles and gain circles.
Chose the impedance and then play with it.
The circuit presented was tuned to lose minimum on NF and Gain. The circuit is placed at the output of the LNA, and luckily the initial instability was not so bad.
One thing that should remember is, if a circuit presents potential instability, doesn’t mean will oscillate. Depends by series of factors, as input/output impedances at particular frequencies.
There are hundreds of articles or RF books that present LNA impedance matching. Just read few of them.
The circuit presented was tuned to lose minimum on NF and Gain. The circuit is placed at the output of the LNA, and luckily the initial instability was not so bad.
One thing that should remember is, if a circuit presents potential instability, doesn’t mean will oscillate. Depends by series of factors, as input/output impedances at particular frequencies.
There are hundreds of articles or RF books that present LNA impedance matching. Just read few of them.
heu vfone may have your chat id....i have many question about the LNA designing..it will be a great help for me to understand this area properly.....
Added after 1 hours 43 minutes:
Well this is the image for the circuit i made to stabilize the LNA.When i increase the value of feedback resistor the value of k increases.can i use this configuration to stabilize the circuit??