Formulas & Data:
- Electronics
- Mathematics
- Physics
- RF & Microwaves

Parts Vendors:
- all hand-selected

- Amateur Radio
- Vintage Articles:
- Electronics World
- Popular Electronics
- QST
- Radio & TV News
- Radio Craft
- Short Wave Craft
- Wireless World

- Events Calendar
RF Cafe Homepage
Copyright 1999-2015   •−•  ••−•    −•−•  •−  ••−•  •   "RF Cafe" in Morse Code  >> Listen to It <<
- EW & Radar Handbook
- Quizzes       - Software
- App Notes
- Calculators
- Advertise on RF Cafe
- About RF Cafe™
- RF Cafe Shirts & Mugs
- RF Cafe Archives
RF Cafe Book Contest
- RF Cafe on Visit RF Cafe on Facebook Visit RF Cafe on Twitter Visit RF Cafe on LinkedIn
- Tech Humor
- Forums Archive
- Job Board
- Donate to RF Cafe
- Kirt's Cogitations
Custom Search
More than 10,000 searchable pages indexed.
Greetings: There is so much good stuff on RF Cafe that there is no way to list or link to all of it here. Please use the Search box or the Site Map to find what you want - there is a good chance I have it. Thanks!

More Stability Circles Questions - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


IR1
Post subject: Stability Circles
Unread postPosted: Tue Jul 13, 2004 9:28 am

Hi,

I have a question regarding stability circles: Do these circles include the impedances which gives reflection coefficients greater than 1: S11>1, S22>1?

The intersection of these circles with the Smith chart gives the areas of instability, matching of the network (e.g Amplifier) to these regions should be avoided...Does this fit to my question above?

Many thanks,
IR1


Top


Jeanalmira
Post subject:
Unread postPosted: Tue Mar 15, 2005 5:20 am

Hi,

For designing amplifers and oscillators, the stability of the two
port network must be considered. Oscillation is possible if either
the input or output port impedance has a negative real par ;this
would imply that gamma in >1 or gamma out >1. In case of assume S12=0 : S11 >1 and S22 >1.

While there are 2 types of stable conditions :
1. Unconditionally stable : where gamma in and gamma out are less or equal to 1; K <1 and delta <1.

2. Potentially unstable (Conditional stability)
The network is conditionally stable if
gamma in is less or equal to 1 and gamma out is less or equal to 1 only for a certain range of passive source and load impedances.

Then, back to your questions on stability circles.
1. Output stability circles can be determined by set gamma in =1.
2. Input stability circles can be determined by set gamma out =1.

the stability circles can represent S11 >1 and S22 >1. It depends on the conditions. But one thing to remember that inside smith chart, S11 and S22 <1.

any doubts or feedback are welcome.
Hope it helps.. :D

Sincerely,
Jean







Posted  11/12/2012

Your RF Cafe
Progenitor & Webmaster

Click here to read about RF CafeKirt Blattenberger… single-handedly redefining what an engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5th MOB: My USAF radar shop

Airplanes and Rockets: My personal hobby website

Equine Kingdom: My daughter Sally's horse riding website