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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Mon Sep 24, 2012 4:17 am Post subject:
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Hi
If you have a DVM with the diode testing function you can just use this function to measure the Vbe voltage drop of your transistors and select those that don't differ by more than 2mV. Otherwise you can build this simple tester I described here :
http://electro-music.com/forum/viewtopic.php?highlight=transistor+matching&t=34177
For your pot problem, a simpler solution is to use the 50K pot without adding a parallel resistor that would change the response curve of the pot. Instead you may simply change the value of R13 to 56K and R14 to 10K. _________________ Yves |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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Posted: Mon Sep 24, 2012 12:03 pm Post subject:
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i found another way...
can you advice me please, can i use +/-12V instead of +/-15V? please see attached pics .
if yes, do i need to modify any resistors value?
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_________________ http://www.myspace.com/mgmtrance |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Mon Sep 24, 2012 12:05 pm Post subject:
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Yes this is the voltage drop of the diode junction between base and emitter and as such corresponds to Vbe. 637 means 637mV. If your transistors are within 637 to 639 then this is OK they are matched.
Concerning the schemo you can use 9V, 12V or 15V it does not matter provided that you run the comparison with same voltage source no need to change th resistor value and obviously we are dealing with DC here _________________ Yves |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
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Posted: Mon Sep 24, 2012 12:17 pm Post subject:
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you are a life saver! thank you very much!
you dont know how frustrating it is to not know electronics and want to build the world
but hey... i'm learning
last question...
does the HFE needs to be matched as well?
infect...in what situation i need a Vbe matched and in what situation i need HFE matched?
are there modules that need both Vbe and HFE matching? _________________ http://www.myspace.com/mgmtrance |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Mon Sep 24, 2012 12:21 pm Post subject:
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HFe is only involved when gain amplification is at stack, Vbe matching is involved for low current application such as current mirrors and differential input stages. _________________ Yves |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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