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Gain of Class AB Vs. Class A - 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.



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.


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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


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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
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