Mpp - Page 208

Joachim Gerhard · 18th January 2011, 11:36 AM

Well, i will do a schematic. Then it is easier to discuss. Actually the changes cost virtually nothing. Just a few more parts to make the current mirror faster, more balanced and lower in distortion.

Joachim Gerhard · 10:57 PM

Rüdiger, this are the improvements i made : i put in two helper resistors. Because they would starve a bit only on the base current i feed them with aproximately 2mA of iddle current. I put in R3. When the same current flows in the left and right side of the mirror no current flows in R3. If there is a mismatch the resistor comes into action and provides differential feedback. i set it arbitrary to 100kOm. In praxis it has to be checked if that value is low enough. It reduces the impedance of the mirror some but it also provides matching and distortion cancelation so i think it is an improvement. I have seen parts of this circuit elsewhere but not implemented in total so i call it a Gerhard Mirror. I have drawn only one side and you have to scroll down a bit to see it. This circuit is much faster and lower in distortion then the simple cascoded mirror and gives an amasing gain in dynamics and slamm.

Onvinyl · 18th January 2011, 01:20 PM

Thanks Joachim. I'll check in out in an update!

Rüdiger

Joachim Gerhard · 18th January 2011, 01:38 PM

Lets see what comes out of that. Good luck.

Joachim Gerhard · 18th January 2011, 01:40 PM

Errata : "helper resistors " should read "helper transistors"

Onvinyl · 18th January 2011, 01:54 PM

Oh no! it even sims at only 1/5 the distortion. Now look what you've done!

Rüdiger

Joachim Gerhard · 18th January 2011, 02:47 PM

Yes, i am bad (:

janneman · 18th January 2011, 03:20 PM

Quote:

Originally Posted by Joachim Gerhard

Yes, i am bad (:

jan didden

Benedetto · 18th January 2011, 05:28 PM

He's back,
celebrate, J is back.

Audiofanatic · 18th January 2011, 05:43 PM

Audiofanatic

18th January 2011, 12:38 PM	#2072
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Rüdiger, this are the improvements i made : i put in two helper resistors. Because they would starve a bit only on the base current i feed them with aproximately 2mA of iddle current. I put in R3. When the same current flows in the left and right side of the mirror no current flows in R3. If there is a mismatch the resistor comes into action and provides differential feedback. i set it arbitrary to 100kOm. In praxis it has to be checked if that value is low enough. It reduces the impedance of the mirror some but it also provides matching and distortion cancelation so i think it is an improvement. I have seen parts of this circuit elsewhere but not implemented in total so i call it a Gerhard Mirror. I have drawn only one side and you have to scroll down a bit to see it. This circuit is much faster and lower in distortion then the simple cascoded mirror and gives an amasing gain in dynamics and slamm. Last edited by Pano; 18th January 2011 at 10:57 PM.

18th January 2011, 01:20 PM	#2073
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	Thanks Joachim. I'll check in out in an update! Rüdiger __________________ "I can feel what's going on inside a piece of electronic equipment. I have a sense that I know what's going on inside the transistors." Robert Moog

18th January 2011, 01:54 PM	#2076
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	Oh no! it even sims at only 1/5 the distortion. Now look what you've done! Rüdiger __________________ "I can feel what's going on inside a piece of electronic equipment. I have a sense that I know what's going on inside the transistors." Robert Moog

18th January 2011, 05:43 PM	#2080
Audiofanatic diyAudio Member Join Date: Oct 2002 Location: The Netherlands, Utrecht	Joachim Audiofanatic __________________ Be nice to animals.

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18th January 2011, 11:36 AM	#2071
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Well, i will do a schematic. Then it is easier to discuss. Actually the changes cost virtually nothing. Just a few more parts to make the current mirror faster, more balanced and lower in distortion.

18th January 2011, 01:38 PM	#2074
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Lets see what comes out of that. Good luck.

18th January 2011, 01:40 PM	#2075
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Errata : "helper resistors " should read "helper transistors"

18th January 2011, 02:47 PM	#2077
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Yes, i am bad (:

18th January 2011, 05:28 PM	#2079
Benedetto diyAudio Member Join Date: Nov 2007 Location: Knifetown-Germoney	He's back, celebrate, J is back.

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