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Old 1st November 2012, 01:27 PM   #1
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Default Are these ok for usage in a vas / current source ?

I'm looking at using a complementary pair of these transistors in a classic vas with currentsource setup. The original uses bd139/140 pair. The specs look ok to me ....
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Old 1st November 2012, 01:57 PM   #2
AndrewT is offline AndrewT  Scotland
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100Vce0, 1A, 550mW, >150 hFE, 7.5pF Cob@10Vcb, >100MHz @ 50mA !!!!! and preponderance of sat data.

The hFE holds up very well at low currents, but all else seems to point to switching duty,
where efficiency of power transfer over rules everything.
It may turn out to be very suitable if the Cob can be tolerated.

For VAS duty, I would look for higher hFE, lower Cob, lower current rating (100mA to 200mA) in exchange for a higher fT and higher Vce0.
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Old 1st November 2012, 09:17 PM   #3
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Ok, thanks !
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Old 1st November 2012, 09:19 PM   #4
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Quote:
Originally Posted by chriscam View Post
I'm looking at using a complementary pair of these transistors in a classic vas with currentsource setup. The original uses bd139/140 pair. The specs look ok to me ....
B139/140 have been used many times in designs for VAS and current source.
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Old 1st November 2012, 09:22 PM   #5
jcx is offline jcx  United States
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A community dedicated to helping everyone learn the art of audio. Projects by fanatics, for fanatics! - Search Results for vas transistor

http://www.diyaudio.com/forums/gtsea...+vas&sa=Search

Last edited by jcx; 1st November 2012 at 09:25 PM.
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Old 2nd November 2012, 03:39 AM   #6
CBS240 is offline CBS240  United States
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Driver transistor, perhaps. VAS, not so good.
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Old 2nd November 2012, 07:22 AM   #7
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I did search using the search forums option which obviously doesn't work as well as the google option. Hmm, anyway, I found a whole bunch of usefull info, reading...

Thanks for pointing !
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