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Re: [Amps] Transistor Bias

To: "GGLL" <nagato@arnet.com.ar>,"Amplificadores Lineales" <amps@contesting.com>
Subject: Re: [Amps] Transistor Bias
From: "Dr. William J. Schmidt, II" <bill@wjschmidt.com>
Reply-to: "Dr. William J. Schmidt, II" <bill@wjschmidt.com>
Date: Sat, 18 Oct 2003 12:06:20 -0500
List-post: <mailto:amps@contesting.com>
You can find them here:
http://www.communication-concepts.com/application_notes.htm ... check the
EB104, which I recall has 4 power devices...

Sincerely,

Dr. William J. Schmidt, II  K9HZ

"Collector of Edison Wind-up Phonographs... Do you have one for me?"
Email: bill@wjschmidt.com
Alternate Email: wmschmidt@charter.net
WebPage: www.wjschmidt.com



----- Original Message ----- 
From: "GGLL" <nagato@arnet.com.ar>
To: "Amplificadores Lineales" <amps@contesting.com>
Sent: Saturday, October 18, 2003 7:39 AM
Subject: Re: [Amps] Transistor Bias


    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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