Does NFmin in cascode LNA depend on the negative feedback inductance?

In summary, the value of NFmin in cascode LNA is directly affected by the negative feedback inductance, with higher inductance resulting in lower NFmin and improved performance. The negative feedback inductance also plays a crucial role in stabilizing the LNA and there is an optimal value for it determined through simulations. It can be replaced with other components, but inductors are preferred for their low loss and high Q characteristics. The negative feedback inductance also helps to reduce the noise figure of cascode LNA.
  • #1
anhnha
181
1
Hi,
This is a cascode LNA. Please help me with the question in picture. Thank you.

attachment.php?attachmentid=66772&stc=1&d=1392802595.jpg
 

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  • #2
What are your thoughts on the question? Is this for school?
 
  • #3
No, I am designing a LNA not a homework.

I read some books and papers saying that NFmin in two cases are equal. However, I would like to understand clearly why and read a decent proof.
Do you have ideal how to prove that?
Thanks.
 
Last edited:

FAQ: Does NFmin in cascode LNA depend on the negative feedback inductance?

1. Does the value of NFmin in cascode LNA change with the negative feedback inductance?

Yes, the value of NFmin in cascode LNA is directly affected by the negative feedback inductance. As the negative feedback inductance increases, the value of NFmin decreases, resulting in better overall performance of the LNA.

2. How does the negative feedback inductance impact the stability of cascode LNA?

The negative feedback inductance plays a crucial role in stabilizing the cascode LNA. It helps to reduce the gain and phase variations caused by parasitic capacitances, thus improving stability and preventing oscillations.

3. Is there an optimal value for the negative feedback inductance in cascode LNA?

Yes, there is an optimal value for the negative feedback inductance in cascode LNA. It is typically determined through simulations and depends on the specific design parameters and requirements of the LNA.

4. Can the negative feedback inductance be replaced with other components in cascode LNA?

Yes, the negative feedback inductance can be replaced with other components, such as resistors or capacitors, to achieve similar effects. However, inductors are preferred for their low loss and high Q characteristics.

5. How does the negative feedback inductance affect the noise figure of cascode LNA?

The negative feedback inductance has a significant impact on the noise figure of cascode LNA. It helps to reduce the noise figure by providing a lower impedance path for the input signal, thus reducing the overall noise contribution from the transistors.

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