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Re: [Amps] Transistor Bias

To: Amplificadores Lineales <amps@contesting.com>
Subject: Re: [Amps] Transistor Bias
From: GGLL <nagato@arnet.com.ar>
Date: Sat, 18 Oct 2003 09:39:14 -0300
List-post: <mailto:amps@contesting.com>
Hello Gene, you may try also another circuit, you can find it at a Motorola application note (sorry, but don't remember which, perhaps in a 300 watts out linear schematic?, maybe someone else in the list know which), it uses an MC1723 ic regulator, and also has implemented thermal compensation. For what you state, your circuit does not have thermal compensation and this seems to me to be practical for correct linear operation.
You can modify bias current also.


Best regards
Guillermo - LU8EYW.

Gene Bigham escribió:

I have been looking at various bias supplies for the 2sc2879 transistor.
I am going to run 4 of them in my amp.  An appealingly simple diagram shows a 
7808 (8v @ 1 amp) regulator supplying bias for a pair of these transistors.  
Anyone with any experience with this sort of set up?  I could easily put two 
7808's in my circuit to feed the center tap of the input transformer to each 
pair of 2sc2879s.  The circuit I am looking at has an output resistor on the 
7808 of 8.2 ohms and a choke in series to the center tap, and also two 
resistors shunting one rated 1 ohm the other labeled TBD (is that to be 
defined?)  This is on a Telstar Electronics schematic for what is identified as 
a Skywave 2879AB.
Any comments about this arrangement?
Thanks
Gene Bigham KB0GU
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