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Design >> RF Design >> broadband or narrowband match in LNA
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Message started by baab on Dec 7^th, 2013, 11:26am

Title: broadband or narrowband match in LNA
Post by baab on Dec 7^th, 2013, 11:26am

Hi,

I need your help again. If I design a LNA with bandwidth = 20MHz, what kind of matching that I need, broadband or narrowband match?

Title: Re: broadband or narrowband match in LNA
Post by aaron_do on Dec 7^th, 2013, 6:26pm

Hi baab,

It depends on the center frequency. For your 1.7 GHz center, 20 MHz is very very narrowband. You need to design your bandwidth so that it accounts for variation in the network's center frequency.

Aaron

Title: Re: broadband or narrowband match in LNA
Post by baab on Dec 7^th, 2013, 7:23pm

Hello Aaron,

Now I switched to fc = 1.555GHz. Based on your answer, I guess it is also narrowband, right?

Quote:

You need to design your bandwidth so that it accounts for variation in the network's center frequency.

May I know what cause the variation?
By the way, I am reading the book you recommended "The Design of CMOS Radio-Frequency Integrated Circuits" by Thomas H. Lee. It is much easier than Razavi book.

Title: Re: broadband or narrowband match in LNA
Post by aaron_do on Dec 8^th, 2013, 6:41pm

For the LC tank, I suppose process and the accuracy of your modeling would be the biggest errors. Of course part of the LC tank would be made up of your transistor capacitances which are subject to voltage and temperature variation.

Aaron