dac I/V convertion with very low distortion - Page 23

smms73 · 17th August 2012, 10:45 PM

Quote:

Originally Posted by Joachim Gerhard

Yes, Patrick, on the surface it looks like the Leach but the bias transistors do something different.

I'm afraid it won't work the way you intend. It work with low distortion in my circuit because don't have voltage variations in the input transistors. the cen topology unfortunately have voltage variation in the input transistors.

Joachim Gerhard · 17th August 2012, 10:48 PM

So when i reduce the circuit to the input stgae i nead a plus-minus supply with regulation ?

EUVL · 17th August 2012, 10:51 PM

A cascode would help.

Patrick

smms73 · 17th August 2012, 10:56 PM

Quote:

Originally Posted by EUVL

A cascode would help.

Patrick

I think so. but we have to take care of the base currents of the cascade. The final circuit will be more complex that your version of the cen.

Shinja · 17th August 2012, 10:58 PM

Quote:

I think the distortion is caused by Cob and Zout of Q1/Q4/Q13/Q14 ,not base current.

I made a mistake.
not Q1/Q4/Q13/Q14,but Q2 and Q5.
then,the distortion will reduce with bootstraping their collector.

Joachim Gerhard · 17th August 2012, 10:58 PM

At the cost of some complexity it could be a voltgae in - current out mirror but then we come closer to component count of the original design.

smms73 · 17th August 2012, 10:59 PM

Quote:

Originally Posted by Shinja

I think the distortion is caused by Cob and Zout of Q1/Q4/Q13/Q14 ,not base current.

Forgot to say that you right

dirkwright · 17th August 2012, 11:02 PM

Seems to work fine to me. I simplified a little.

smms73 · 17th August 2012, 11:07 PM

Quote:

Originally Posted by Shinja

I made a mistake.
not Q1/Q4/Q13/Q14,but Q2 and Q5.
then,the distortion will reduce with bootstraping their collector.

Do a simulation. IM with a Android phone only don't have my computer. And post your results .

smms73 · 17th August 2012, 11:12 PM

Dirkwright it works but not with the very low distortion that my circuit is capable. Joachim wants to achieve my distortion levels with the simplicity of the
cen topology

17th August 2012, 10:51 PM	#223
EUVL diyAudio Member Join Date: Oct 2003	A cascode would help. Patrick __________________ xen-audio.com

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17th August 2012, 10:48 PM	#222
Joachim Gerhard diyAudio Member Join Date: Mar 2009	So when i reduce the circuit to the input stgae i nead a plus-minus supply with regulation ?

17th August 2012, 10:58 PM	#226
Joachim Gerhard diyAudio Member Join Date: Mar 2009	At the cost of some complexity it could be a voltgae in - current out mirror but then we come closer to component count of the original design.

17th August 2012, 11:12 PM	#230
smms73 diyAudio Member Join Date: Jul 2005 Location: Lisboa, Portugal	Dirkwright it works but not with the very low distortion that my circuit is capable. Joachim wants to achieve my distortion levels with the simplicity of the cen topology