How to get the stability for the microwave lownoise amplifier

[btv_murthy]

Dear sir,
I have designed microwave low noise amplifier , used self bias . I am getting the k =0.29086 and B1= 1.546. How to adjust the stability, Can you help me anybody.

 

[tony_lth]

There are many ways to do so. Such as add a little L between the emitter and GND, or add a series resistor on the output circuits.
Could you upload your sch?

 

[btv_murthy]

Dear Sir,
Is there any good book to read about achieve stability of the microwave low noise amplifier

 

[jeffrey samuel]

try to find more about this in David A Bell's book of electronic devices and circuits
it describes a lot about mid band analysis
very helpful in stability terms

 

[btv_murthy]

Dear Sir,
I am asking about the microwave frequency range ( 1 GHz to 1.5 GHz) stability good book.

 

[jeffrey samuel]

https://books.google.co.in/books/about/Broadband_Microwave_Amplifiers.html?id=awLC616gPsMC&redir_esc=y

check this out

 

[btv_murthy]

tony Sir,
For designing the LNA ( frequency range 1 GHz to 1.5GHz), I used drain resistance Rd= 135 ohm, source resistance Rs= 2 ohm, resistance between drain and source Rds= 2000 ohm . I set Vds =1.78v, Id= 24.1mA, Vgs = -0.2V , L= 8nH. I got the NF =0.26596 S(2,1) = 7.1786 at 1.3 GHz. I achieved NF and Gain without connecting feed back resistor between gate and drain . When I connected the feedback resistance between gate and drain R=340 ohm, I am getting the NF more and Gain very less NF=1.2314dB, Gain= 3.4314. What I have to do for getting NF lessthan 0.3 dB and Gain more than 7 mag with achieving the stability. If I don't connect the resistance , was getting NF less than 0.3 dB and Gain more 7 mag without achieving stability, but once I connect the feedback resistance between drain and gate Rdg=340, achieve the stabilty , but loosing NF and Gain. Can u help me , How to get out from this problem. I used the transistor NEC3508 nonlinear .

 

[tony_lth]

I used FHX series LNA for 9.6G LNA, get 0.6dB NF and more than 12dB gain. I suggest you use FHC40LG, you should get NF 0.4dB at most, and gain 12dB at least. 1st try to do the smith chart match in the input for the low noiseand conjugate match for the max gain. I think an LC match for the input is enough. You should so all the simulation with ADS and AWR etc. Momentum simulation is needed and RLC library model is needed also.

 

[young.microwave.eng]

hi
please attach you schematic and then it is better situation to discuss.It seems that drain resistance is too high to reach that value of noise figure.and of course the feedback resistor(drain to source) is connected for gain flatness usually.If the gain is flat enough you can omit that value of resistance.and about the stability have you checked the stability practically or you guess it using formula?
please connect the output to spectrum analyzer and see the spectrum and at the same time check the S11 and S22 using network analyzer.maybe your amplifier is stable enough and again you can omit some resistors too.
If your amplifier is not stable then there is some oscillations in different frequencies and you can not achive your desired gain.so please chech your gain too

 

[ltrlspree]

tony Sir,
For designing the LNA ( frequency range 1 GHz to 1.5GHz), I used drain resistance Rd= 135 ohm, source resistance Rs= 2 ohm, resistance between drain and source Rds= 2000 ohm . I set Vds =1.78v, Id= 24.1mA, Vgs = -0.2V , L= 8nH. I got the NF =0.26596 S(2,1) = 7.1786 at 1.3 GHz. I achieved NF and Gain without connecting feed back resistor between gate and drain . When I connected the feedback resistance between gate and drain R=340 ohm, I am getting the NF more and Gain very less NF=1.2314dB, Gain= 3.4314. What I have to do for getting NF lessthan 0.3 dB and Gain more than 7 mag with achieving the stability. If I don't connect the resistance , was getting NF less than 0.3 dB and Gain more 7 mag without achieving stability, but once I connect the feedback resistance between drain and gate Rdg=340, achieve the stabilty , but loosing NF and Gain. Can u help me , How to get out from this problem. I used the transistor NEC3508 nonlinear .

let us see the schematic for simplicity.
fyi, the MWJ has compiled quite decently some tips on stability last months, see below link
https://www.microwavejournal.com/articles/17865-expert-tips--tricks-and-techniques-
(Stable as a Rock portion)


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[Abhishekabs]

Mr. Murthy,
There is a book.
microwave transistor amplifiers by gonzalez.
Its very awesome book to start with, very simple explanations & good for beginner.
It explains how to design stable uWave amplifier.

Now for stabilizing amplifier, there are many practical hints you will find in ARRL books.
You have to see which one applies to your circuits.
Its black magic so you have to try on your own.

 

[btv_murthy]

Dear Sir,
I have gone througth the Gonzalez, You told some book to go througth about ARRL books, I did not get what is ARRL , can u tell me in detail what is ARRL, I will search it, can get answer for my stability.

 

[tony_lth]

The American Radio Relay League (ARRL) handbooks 2001 version