Discrete buffer notion

Sheldon · 9th September 2009, 05:02 AM

Apologies to Joe Rasmussen and Allen Wright for this variation on the Super Linear Follower. But wondering if it might work with a BJT on top?

Sheldon

Lumba Ogir · 9th September 2009, 06:35 AM

Hi,
would this work?

Wavebourn · 9th September 2009, 08:07 AM

Quote:

Originally Posted by Sheldon

Apologies to Joe Rasmussen and Allen Wright for this variation on the Super Linear Follower. But wondering if it might work with a BJT on top?

Actually, it is a variation of my Tower power stage.

No, such a way it will not work. You need to add some voltage on the base, instead of dropping it. Use one CCS fro + rail to base, and a resistor from base to output of the source follower.

Or, one Zener from output to base, and one resistor to B+

Sheldon · 9th September 2009, 02:46 PM

Thanks.

Quickly drew this up before going to bed, and thought I could eliminate the resistors. Somehow it didn't seem right, which is why I posted the question. Realize now, as Wavebourn notes, that I was looking at the voltage drop backwards. Sometimes tripped up on errors too obvious to see.

I like Lumba's LED approach, as it eliminates a cap, plus it lights up. Is there any advantage to a BJT in the top position, as compared to an FET? I guess I'd use a higher beta device than the 5551.

Sheldon

Wavebourn · 9th September 2009, 03:20 PM

If you like LEDs you may want to use one more, to give a little bit more of voltage between drain and source.

Lumba Ogir · 10th September 2009, 01:23 PM

Sheldon,
It should be a BJT in the top position.

Sheldon · 10th September 2009, 03:22 PM

Thanks.

Might be a good simple example to motivate me to learn LT Switcher CAD.

Sheldon

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9th September 2009, 02:46 PM	#4
Sheldon diyAudio Member Join Date: Dec 2003 Location: San Diego	Thanks. Quickly drew this up before going to bed, and thought I could eliminate the resistors. Somehow it didn't seem right, which is why I posted the question. Realize now, as Wavebourn notes, that I was looking at the voltage drop backwards. Sometimes tripped up on errors too obvious to see. I like Lumba's LED approach, as it eliminates a cap, plus it lights up. Is there any advantage to a BJT in the top position, as compared to an FET? I guess I'd use a higher beta device than the 5551. Sheldon

9th September 2009, 03:20 PM	#5
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	If you like LEDs you may want to use one more, to give a little bit more of voltage between drain and source.

10th September 2009, 01:23 PM	#6
Lumba Ogir Banned Join Date: Apr 2005 Location: Stockholm	Sheldon, It should be a BJT in the top position.

10th September 2009, 03:22 PM	#7
Sheldon diyAudio Member Join Date: Dec 2003 Location: San Diego	Thanks. Might be a good simple example to motivate me to learn LT Switcher CAD. Sheldon

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