RF input power of LNA

The input power of my receiver is -100dBm (.1 pw).I want to design LNA using BJT but how can I calculate or recognized that my LNA is able to sense such a small signal at the input.What parameter of the BJT indicate us about the sensitivity of transistor.

You parameter is Noise Figure. Thermal noise is -173.8+10Log10(useful signal bandwith in Hertz). Your LNA can sense signal as waek as those calculated in this way plus the noise figure of the LNA itself.
Bye

hello mrm, can you tell me how the formula you offered comes from or how to deduced it? what is the theory basis?

Look here, it is not directly related, but a good tutorial:

hXXp://www.ctjc.com/tutorial.htm

P.S. Remove the XX and add tt


Mandi

My formula comes from thermodynamic equilibrium: -173.8 is nothing but 10*Log10(Kb*T) where Kb is Boltsman's constant. This formula describes the noise due to the thermal turbulence of electrons inside a conduction band (electron sea model) and is the most accurate. This description fails when describing otherphenomenous like the ones inside a semiconductors. For this reason we introduce noise figure, that describes the degradation in noise performances due to all oter effects but thermodynamics and that is simply a macroscophical parameter. U can fin more in every book on RF design (Gonzaes, Vizmuer etc.)
I hope I've been clear...Bye MRM

My formula comes from thermodynamic equilibrium: -173.8 is nothing but 10*Log10(Kb*T) where Kb is Boltsman's constant. This formula describes the noise due to the thermal turbulence of electrons inside a conduction band (electron sea model) and is the most accurate. This description fails when describing otherphenomenous like the ones inside a semiconductors. For this reason we introduce noise figure, that describes the degradation in noise performances due to all oter effects but thermodynamics and that is simply a macroscophical parameter. U can fin more in every book on RF design (Gonzaes, Vizmuer etc.)
I hope I've been clear...Bye MRM

Hello,

I want a tutorial about the design of BJT LNA, i want to build it with discrete components at freq. ~ 100MHz,

Thanks for help,
Ahmad,

Hi,

I attach some papers about it but if you need schematic
I already have it! (I hope you have orcad)

David

thanks

So you need orcad schematic or genesys simulation?

David