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Old 18th January 2012, 07:32 PM   #1
thanong is offline thanong  United States
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Default LM7812 need to boost current.

greeting everyone,I have positive regulator I.C LM 7812 need to boost output current around 2 ampere.How to add transistor to get that current.I don't want to use 317 series,can anyone please give me simple circuit to wirring will very appreciate ( I use this I.C regulator to heat 12AX7 filament it work fine and sound good enough for my ears but I need more current).Thanks foward.
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Old 18th January 2012, 07:34 PM   #2
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so what about 78S12?
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Old 18th January 2012, 07:43 PM   #3
thanong is offline thanong  United States
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Quote:
Originally Posted by Juergen Knoop View Post
so what about 78S12?
Thanks Juergen,I din't try yet now I'm home a lot of snow around Seattle,Washington USA.I can't go anywhere soon,but I have NPN transistor in hand I just want to try to add transistor to boost current first.
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Old 18th January 2012, 07:57 PM   #4
Puffin is offline Puffin  United Kingdom
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This works well. I have built it.

Click the image to open in full size.

I have used BD139 for Q1.

Full information here

http://www.extremecircuits.net/2009/...r-circuit.html

http://www.extremecircuits.net/p/com...-projects.html

Last edited by Puffin; 18th January 2012 at 08:00 PM.
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Old 18th January 2012, 08:02 PM   #5
thanong is offline thanong  United States
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Quote:
Originally Posted by Puffin View Post
This works well. I have built it.

Click the image to open in full size.

I have used BD139 for Q1.
Hi Puffin,awesome my man this what I really need.Can you give me the value of R1,R2 please.Many thanks.
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Old 18th January 2012, 08:06 PM   #6
thanong is offline thanong  United States
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Originally Posted by thanong View Post
Hi Puffin,awesome my man this what I really need.Can you give me the value of R1,R2 please.Many thanks.
Thank you very much Puffin I got it.It work now.Very appreciate and you have a good evening guy.
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Old 18th January 2012, 08:16 PM   #7
Puffin is offline Puffin  United Kingdom
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If you need 2A you could use an extra transistor like this :-

Click the image to open in full size.
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Old 19th January 2012, 12:49 AM   #8
Enzo is offline Enzo  United States
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Look up some 7812 data sheets. I can;t say for all of them, but some will have basic sample circuits, one of which will be that current boost.

Meanwhile, a 12AX7 at 12v needs 150ma. How many 12AX7s do you have to need 2A for them?
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Old 19th January 2012, 01:54 AM   #9
6L6 is offline 6L6  United States
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thanong -

Can you give us a bit more information? Specifically,

What is this being used in?
What is your voltage supply? (What transformer, rectification, etc...)
What is the load? You mention filaments, what kind of tubes? How many?
You say you want to 'boost the current' Can you elaborate?
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