Constant current

PRBS · 23rd March 2002, 03:48 PM

Does anyone can help me how to implement constant current on BOSOZ?

Freddie · 23rd March 2002, 04:19 PM

Check this out.
http://www.aussieamplifiers.com/se-sch.htm

/Freddie

PRBS · 23rd March 2002, 04:56 PM

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?

Nicke · 23rd March 2002, 10:38 PM

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

djk · 24th March 2002, 11:22 AM

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.

PRBS · 24th March 2002, 12:07 PM

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?

Jens · 24th March 2002, 12:49 PM

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). That’s all.

Jens

23rd March 2002, 03:48 PM	#1
PRBS diyAudio Member Join Date: Mar 2002 Location: Taiwan	Constant current Does anyone can help me how to implement constant current on BOSOZ?

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23rd March 2002, 04:19 PM	#2
Freddie diyAudio Member Join Date: Oct 2000 Location: Sweden	Check this out. http://www.aussieamplifiers.com/se-sch.htm /Freddie

23rd March 2002, 10:38 PM	#4
Nicke diyAudio Member Join Date: Jun 2001 Location: Sweden	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

24th March 2002, 11:22 AM	#5
djk diyAudio Member Join Date: Feb 2001 Location: USA	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.

24th March 2002, 12:07 PM	#6
PRBS diyAudio Member Join Date: Mar 2002 Location: Taiwan	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?

24th March 2002, 12:49 PM	#7
Jens diyAudio Member Join Date: Feb 2001	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). That’s all. Jens