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Old 9th September 2009, 06:02 AM   #1
Sheldon is offline Sheldon  United States
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Default Discrete buffer notion

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
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Old 9th September 2009, 07:35 AM   #2
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Hi,
would this work?
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Old 9th September 2009, 09:07 AM   #3
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Quote:
Originally Posted by Sheldon View Post
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+

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Old 9th September 2009, 03:46 PM   #4
Sheldon is offline Sheldon  United States
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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
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Old 9th September 2009, 04:20 PM   #5
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If you like LEDs you may want to use one more, to give a little bit more of voltage between drain and source.
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Old 10th September 2009, 02:23 PM   #6
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Sheldon,
It should be a BJT in the top position.
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Old 10th September 2009, 04:22 PM   #7
Sheldon is offline Sheldon  United States
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Thanks.

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

Sheldon
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