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20th April 2012, 07:58 AM  #1 
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Join Date: Apr 2012

±45v lm317?

20th April 2012, 08:18 AM  #2  
diyAudio Member

Quote:
An example: for output of 11.25V, you know that there will be 10V across R2+Rv1. (11.25  1.25). 10V is 8 times 1.25V on R1 so R2 + Vr1 = 8 times R1 = 8 times 220 = 1720 ohms. For your 45V you know on R2 + Vr1 is 451.25 = 43.75V, so R2 + Vr1 = 43.75/1.25 * 220 = 7.7k.... For the 45 you can use an LM337 but the calculation is the same. BTW This is also in the datasheet, very simple, you could easily find that yourself without worrying what is true or not. Datasheets are your friend! ;) jan didden
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20th April 2012, 08:22 AM  #3 
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Join Date: Jan 2006
Location: Ireland

Plus there are loads of online calculators to make it even easier. There are also LM317ht that can do 57v

20th April 2012, 08:28 AM  #4  
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Join Date: Apr 2012

Quote:
thany you very much ,i see. 

20th April 2012, 08:38 AM  #5 
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Location: Hangzhou  Marco Polo's 'most beautiful city'. 700yrs is a long time though...
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Beware the inputoutput voltage limit
For any input voltage above 40V, there's no short circuit protection with this device  I've seen at least one explode, so be very wary of shorting the output. On powerup transients too its possible to exceed the abs max.
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22nd April 2012, 08:47 AM  #6 
diyAudio Member

LM783?
/U. 
22nd April 2012, 09:08 AM  #7 
diyAudio Member
Join Date: Nov 2011
Location: UK

You'd be better off building a regulator using discrete components at that voltage.
Have a look at http://www.kkpcb.com for some ideas. 
22nd April 2012, 09:29 AM  #8 
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Join Date: Nov 2011
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22nd April 2012, 02:00 PM  #9 
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Join Date: Apr 2012

agree with KatieandDad
You'd be better off building a regulator using discrete components at that voltage. 
22nd April 2012, 05:29 PM  #10 
diyAudio Member

LM317 can only handle about 1,5A so be carefull on that part, if you need higher current than you will need to add a power tranzistor on it, but as the other have sayd it would be better with zenner diodes and a few transistors to supply the needed current, it would be much safer as you can add the protection you want/need.

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