Matching of 2N3055 and emitors resistoers?

Pigy · 15th January 2007, 08:36 AM

Please,forgive me for my bad english.
I'm from Serbia.
Healp me:
My problem is it:
How matching two pars transistors 2N3055 in audio amplifier.
I know this possible with matching transistors,their gain Hfe,but if gain is not homologous (seem) ,uses emitors resistors examp.0,1-0,47 oms.
It is true?
Which size of oms is ok for this.
Why is uses milioms resistors in emitor of transistors(output transistors)?
Please see my shematics and your comomment?

ps: T6,T7 is 2N3055,T4/T5 drivers BC286/287,R16,R17 0,47 oms.

peranders · 15th January 2007, 10:33 AM

I this design I can't imagine that you'll need to match the output transistors.

Emitter resistors are usually in the range you describe and this for creating a voltage drop of 0.3 1.0 V. This voltage is used for controlling the working conditions of the transistor especially when it gets hot. If you don't have these resistors the transistor will draw more current -> hotter -> even more current -> even more hot -> more more ->

->

undaunted · 19th January 2007, 05:55 PM

For a test circuit to match dc current gain of transistors, look here:

http://users.ece.gatech.edu/~mleach/lowtim/part2.html

Pigy · 22nd January 2007, 08:37 AM

Thanks friends,but who value of resisitors is possible for god job of transisitors.In many schematics value is 0.1-0.47 ohm.What's your suggestion?

15th January 2007, 10:33 AM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	I this design I can't imagine that you'll need to match the output transistors. Emitter resistors are usually in the range you describe and this for creating a voltage drop of 0.3 1.0 V. This voltage is used for controlling the working conditions of the transistor especially when it gets hot. If you don't have these resistors the transistor will draw more current -> hotter -> even more current -> even more hot -> more more -> -> -> -> -> -> __________________ /Per-Anders (my first name) or P-A as my friends call me

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19th January 2007, 05:55 PM	#3
undaunted diyAudio Member Join Date: Jan 2007	For a test circuit to match dc current gain of transistors, look here: http://users.ece.gatech.edu/~mleach/lowtim/part2.html

22nd January 2007, 08:37 AM	#4
Pigy diyAudio Member Join Date: Nov 2006 Location: Pozega,Serbia	Thanks friends,but who value of resisitors is possible for god job of transisitors.In many schematics value is 0.1-0.47 ohm.What's your suggestion?

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