Thank you for visiting RF Cafe! Electronics World Cover,TOC,and list of posted Popular Electronics articles QST Radio & TV News Radio-Craft Radio-Electronics Short Wave Craft Wireless World About RF Cafe RF Cafe Homepage RF Cafe in Morse Code Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs Twitter LinkedIn Crosswords Engineering Humor Kirt's Cogitations Engineering Event Calendar RF Engineering Quizzes AN/MPN-14 Radar 5CCG Notable Quotes App Notes Calculators Education Magazines Software,T-Shirts,Coffee Mugs Articles - submitted by RF Cafe visitors Simulators Technical Writings RF Cafe Archives Test Notes Wireless System Designer RF Stencils for Visio Shapes for Word Search RF Cafe Sitemap Advertising Facebook RF Cafe Forums RF Cafe Homepage Thank you for visiting RF Cafe!

LNA Designing Help! - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement

Post subject: LNA designing help! Posted: Sun Aug 07, 2005 9:53 pm


Joined: Tue Aug 02, 2005 1:44 am
Posts: 3
Location: NTU
Hi, regarding to several topologies of designing a LNA? The inductive degenation of common source should be the most popular one right now, but the limitation is the high voltage and not so good isolation. The common gate could be better in applying low voltage and good isolation, as well as input matching. Why few people use common gate topologies? If I want to design a low voltage(<1.0v) low power, narrowband RF LNA (abt 2.45GHz), among all the topologies, which could be more suitable for me to choose? Can you give me some suggestions? Thanks very much.


Post subject: common gatePosted: Mon Aug 15, 2005 1:28 am


Joined: Mon Aug 15, 2005 12:55 am
Posts: 6
My experience with common gate/base LNAs are that they tend to be more unstable than the standard common source topology. The biasing bypass on the gate/base is very sensitive to parasitic inductances which tend to be a pain.

You will have a hard time using a FET based technology for under 1V. A bipolar might have a better chance of working (SiGe).


Post subject: LNAPosted: Mon Aug 15, 2005 11:51 am
The experience reported by "uwavegeek" matches mine.

However, your thoughts about common-gate circuits are in fact valid at lower frequencies (VHF/UHF), where you can actually reduce parasitics to a low-enough level.

Uwavegeek is also right about the 1V issue. It will even be difficult to do a really good job with SiGe or other bipolar technology.

Good Luck!

Posted  11/12/2012

RF Cafe Software

   Wireless System Designer - RF Cafe
Wireless System Designer

RF & EE Symbols Word
RF Stencils for Visio
Calculator Workbook
RF Workbench
Smith Chartâ„¢ for Visio
Smith Chartâ„¢ for Excel

About RF Cafe

Kirt Blattenberger - RF Cafe WebmasterCopyright
1996 - 2022
Kirt Blattenberger,

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:

Try Using SEARCH
to Find What You Need. 
There are 1,000s of Pages Indexed on RF Cafe !