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Old 23rd March 2002, 04:48 PM   #1
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Question Constant current

Does anyone can help me how to implement constant current on BOSOZ?
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Old 23rd March 2002, 05:19 PM   #2
Freddie is offline Freddie  Sweden
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Check this out.
http://www.aussieamplifiers.com/se-sch.htm

/Freddie
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Old 23rd March 2002, 05:56 PM   #3
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Quote:
Originally posted by Freddie
Check this out.
http://www.aussieamplifiers.com/se-sch.htm

/Freddie
Thank you Freddie. I am not familiar with active constant current. If I want to creat 40 mA constant current, how should I do?
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Old 23rd March 2002, 11:38 PM   #4
Nicke is offline Nicke  Sweden
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Read this thread for info about constant current source:

paralleling mosfets in BLS

And read the article about DIY opamps at (there you can find how to make constant current sources) :

http://www.passdiy.com/legacy.htm

/Nicke
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Old 24th March 2002, 12:22 PM   #5
djk is offline djk
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With reference to this figure: http://www.aussieamplifiers.com/se-sch.htm "If I want to creat 40 mA constant current, how should I do?" R8,9 cause Q3 to turn on.When the voltage across R10 reaches the base/emitter threshold voltage of Q4 the current becomes constant.Thus a beV of 0.6V divided by an R10 of 10 ohms would give 60mA.
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Old 24th March 2002, 01:07 PM   #6
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Thank you djk, I understood that already.

Does the gain of that circuit reflects R1+R2 divided by R3+R4?
That means, 2k ohms/440 ohms aorund 4.55. Am I right?
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Old 24th March 2002, 01:49 PM   #7
Jens is offline Jens  Germany
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Alternatively, use four LM317 with 30R resistors (for ~40mA) between pin Adj.(1) and Out(2), connect pin In(3) to the S of Q1/Q2 and pin Adj(1) to R17 (-V). Thatís all.

Jens
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