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

Parts Vendors:
- all hand-selected

- Amateur Radio
- Vintage Articles:
- Electronics World
- Popular Electronics
- 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!

P1 dB - 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.

Post subject: P1 dB Posted: Wed Nov 29, 2006 3:01 am


Joined: Tue Oct 03, 2006 3:03 am
Posts: 11
Location: India
What is the need and significance of P1 dB point in the amplifier design


Post subject: Posted: Wed Nov 29, 2006 7:48 am

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
P1dB gives an indication of the output power to which the amplifier is capable to deliver before going into saturation.

Before the amplifier reaches the P1dB it behaves linearly that means a linear relation between its input power and output power. So if you increase the input power by 1dB the output power will increase in 1dB as well.

The amplifier doesn't enter sharply into the P1dB area. The output power becomes non-linear before this point reaches. The gain will decrease gradually from the linear gain G (Measured in small signal) to G-1dB. This can be seen if you increase the input power dB by dB until you will reach the G-1dB point in which the output power will be the P1dB [dBm]

Best regards,

- IR


Post subject: Posted: Wed Nov 29, 2006 6:03 pm


Joined: Wed Nov 29, 2006 5:51 pm
Posts: 2
Actually the more precise definition is the power at which the power response deviates from the linear response by 1 dB.

In other words for instance when you have an amplfier that has a gain of say 10 db you will see a difference between output power and input power of 10 dB in the linear region. As you increase the input power there is a point where the power amplifier starts saturating and the power increases to a point that is less than the 10dB gain expected. In this particular case of 10dB gain the output power at which the power gain is 9dB instead of the expected 10dB is called the "1dB compression point".

Being that the 1dB compression is already deviated from the linear response starting when it starts to compress this area is not really useful for linear transmission. In most cases for acceptable performance you need to back away from this point by 6 to 12 dB.

In most spread spectrum system when using non-linearized amplifiers you usually use the 10dB backoff rule of thumb to get acceptable spectral performance.



Post subject: Why not P2/P3 dB?Posted: Wed Jan 03, 2007 11:48 pm


Joined: Tue Oct 03, 2006 3:03 am
Posts: 11
Location: India
Why not P2/P3 dB?


Post subject: Posted: Fri Jan 05, 2007 5:09 pm

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany

To the best of my knowledge, it is a matter of industry standard definitions.

You can also choose P2dB, P3dB. Actually there is a use for these figures for quantizing the AM/AM curves of PA in order to generate opposite curves for pre-distortion linearization schemes.

Best regards,

- IR

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