Voltage Regulators query
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 23rd January 2006, 09:10 AM #1 Wynand   diyAudio Member     Join Date: Mar 2005 Location: Cape Town Voltage Regulators query If I want to use the LM317/337 to power a preamp, basically just one opamp, would I need a heatsink? The input V will be max 35Vdc
 23rd January 2006, 09:16 AM #2 pinkmouse   diyAudio Moderator     Join Date: Apr 2002 Location: Rotherham, England Didn't you ask this question a while back, or am I going mad in my old age? Dissipated power is a product of the voltage dropped and the current used. For that much voltage drop, even at low current, I would heatsink the regs. Better safe than sorry. __________________ Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
jan.didden
diyAudio Member

Join Date: May 2002
Location: The great city of Turnhout, BE
Quote:
 Originally posted by pinkmouse Didn't you ask this question a while back, or am I going mad in my old age? Dissipated power is a product of the voltage dropped and the current used. For that much voltage drop, even at low current, I would heatsink the regs. Better safe than sorry.

IOW, if the input is 35V, and the output is 15V, dropped V is 20V. With a load of say 25mA (probably less) P = 20 x 25 mW = half a watt. Maybe just a small sink would be wise, as Pinkmouse said.

Jan Didden
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 23rd January 2006, 09:27 AM #4 Wynand   diyAudio Member     Join Date: Mar 2005 Location: Cape Town If I've asked this question before I apologize. I can't remember it though (and I don't even have old age to blame Thanks for the explanations !!!
 23rd January 2006, 09:36 AM #5 pinkmouse   diyAudio Moderator     Join Date: Apr 2002 Location: Rotherham, England No problem Wynand, I'm sure I've done the same thing before! Jan's post gives you the numbers, though I was rather hoping you'd do the maths and get a proper feel for it, then you can use it again in the future. I've found that working out simple questions like this helps a lot to get a feel for a circuit and leads to greater understanding in the long term, and as a relative newbie, I certainly need all the understanding I can get. __________________ Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
jan.didden
diyAudio Member

Join Date: May 2002
Location: The great city of Turnhout, BE
Quote:
 Originally posted by pinkmouse No problem Wynand, I'm sure I've done the same thing before! Jan's post gives you the numbers, though I was rather hoping you'd do the maths and get a proper feel for it, then you can use it again in the future. I've found that working out simple questions like this helps a lot to get a feel for a circuit and leads to greater understanding in the long term, and as a relative newbie, I certainly need all the understanding I can get.

Point taken, Al

Jan Didden
__________________
Music is dither to the brain; lets me think below the usual chaos - me
Linear Audio Vol 13 is out! Check out my Autoranger and SilentSwitcher

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