Gain of Class AB Vs. Class A - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

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

-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews

-- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

lna
Post subject: Gain of Class AB Vs. Class A Posted: Thu Jun 11, 2009 9:56 pm

Captain

Joined: Mon May 04, 2009 6:47 pm
Posts: 22
This maybe a stupid question,

For the same device biased to class A and class AB, Is the gain of class AB about 3dB lower than class A? It seems to me just half of input power being amplified and another half of power being cutoff.

Top

IR
Post subject: Re: Gain of Class AB Vs. Class APosted: Fri Jun 12, 2009 9:10 am

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
The result of lower biasing means lower gain. If the device has the same retrun loss at both ports in both classes, then the gain difference is a matter of the bias level (Idq).

_________________
Best regards,

- IR

Top

Jeanalmira
Post subject: Re: Gain of Class AB Vs. Class APosted: Wed Jul 15, 2009 2:24 am

General

Joined: Tue Mar 15, 2005 11:43 pm
Posts: 65
Location: Singapore
Hi,

Well, I believe the gain here is linear gain. Class A amplifier operates at linear region, which by saying that the linear gain is higher compared to Class AB. The advantage of Class AB is to reduce distortions under nonlinear operations. So Class A and Class AB serves different purposes in applications and they operate under different load lines. Usually at typical cascaded amplifiers, Class A preferable as gain stage (under linear operation/ small signal).

I hope it helps.

Regards,
-Jean

Posted 11/12/2012