« The Drug - John Dunn, Consultant, Ambertec, P.E., P.C. | Main | The Bluest Screen of Death - John Dunn, Consultant, Ambertec, P.E., P.C. »

October 04, 2011

Comments

Account Deleted

Yes, the gain of G1 must be high.. Feedback networks can also be employed to improve the gain (G1)which will help in improving the SNR..

Joel Koltner

One potentially non-obvious point with the simplistic "make G1 high!" approach is that you have to *keep the gain from the input to ALL points in the signal path reasonably high*. I.e., if at any point in the signal path G1*G2*G3*...etc... heads back down to something approaching one, noise again adds directly as if it were present at the source.

This problem is typically seen in (arguably) poorly designed RF front ends, where someone had an overload problem and just added a big attenuator to try to fix it. In fact, the usual problem with designing good front ends is balancing gain distribution with overload protection -- based on presentations such as this one, some people come off with the mistaken idea that "as much gain as possible as soon as possible" is a good idea when, in actuality, if anything it's usually better to give up a little bit of system noise figure and lump the bulk of your gain towards the back end of a system in a "general purpose" receiver so that you have decent dynamic range/overload protection.

Frank Walker

Bandlimiting is of similar importance, I have been privy to more than a handful of designs which had very sensible gain topologies but did not properly tailor the bandwidth at the gain stage.

Noise Figure

Thanks for your sharing this information.
http://www.maurymw.com/MW_RF/Noise_Parameter_Measurements.php

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been saved. Comments are moderated and will not appear until approved by the author. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Comments are moderated, and will not appear until the author has approved them.

Your Information

(Name and email address are required. Email address will not be displayed with the comment.)

Editor

  Learn about our  

 free engineering 

consulting referral 

      service at:

 

  IEEE Consultant's 

      Network of 

     Long Island

 

We have over forty 

electrical, electronic, 

mechanical and 

software engineers 

with expertise in more 

than sixty-five categories 

of technology and business. 

All are members of the 

IEEE and adhere to the 

IEEE professional codes 

of ethics. 

No fee is charged for the

referral service. 

Each member is an 

independent consultant 

and negotiates his/her 

own consulting agreement.

 

Editor: Jerry Brown

Contributors:

John Dunn

Marty Kanner

Murray Kleiner

Dick LaRosa

David Pinkowitz

Carl Schwab

Gerry Bodner

Larry Rachman

 

Unless otherwise noted, 

reprinting or republication 

of anarticle on this blog is 

authorized by crediting the 

author and prominently 

displaying the following 

sentence at the beginning 

or end of the article,

including the hyperlink to

IEEE Consultant's Network 

of Long Island


"This report is republished 

with permission of IEEE 

Consultant's Network of 

Long Island"

 

Pages

Blog powered by Typepad

Enter your email address:

Delivered by FeedBurner