Maximum voltage for LM4780

G.L. Tirebiter · 5th March 2005, 10:56 PM

What is the maxium ps output voltage anyone has so far tried with the LM4780. I have a 35-0-35 transformer on hand, but I don't know if that 's too much. Any thoughts?

DonoMan · 5th March 2005, 11:12 PM

You can use it if you have really good heatsinks

Tweeker · 6th March 2005, 03:23 AM

LM4780 has an absolute limit of +/-42 volts at the rails, or so sayeth the data sheet.

DonoMan · 6th March 2005, 03:24 AM

damn, I'm good at confusing lm4780 for other chips I've seen, lol

G.L. Tirebiter · 6th March 2005, 07:45 AM

I have some small ones I salvaged out of an old amp. Where would one go on the Net to order some big ones?

Thanks in advance.

DonoMan · 6th March 2005, 10:06 AM

It would be +/- 47V max if you have an input (so if you ground the input through a resistor, it may be ok) so says the data sheet, actually (I hadn't realized before that it was for both rails heh) and if your transformer is 35-0-35 then you'd have 49.5V after DC conversion. Options:

1) Try it anyway (bad idea but might be ok with a really big heatsink)
2) Regulate the power supply down to ~40V for voltage (best idea IMO, as regulating has other advantages as well)
3) Modify the transformer
4) Get a new transformer

5th March 2005, 10:56 PM	#1
G.L. Tirebiter diyAudio Member Join Date: Mar 2005 Location: Canada	Maximum voltage for LM4780 What is the maxium ps output voltage anyone has so far tried with the LM4780. I have a 35-0-35 transformer on hand, but I don't know if that 's too much. Any thoughts?

6th March 2005, 07:45 AM	#5
G.L. Tirebiter diyAudio Member Join Date: Mar 2005 Location: Canada	Heat sink supplier? I have some small ones I salvaged out of an old amp. Where would one go on the Net to order some big ones? Thanks in advance.

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5th March 2005, 11:12 PM	#2
DonoMan diyAudio Member Join Date: Feb 2005 Location: Massachusetts	You can use it if you have really good heatsinks

6th March 2005, 03:23 AM	#3
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	LM4780 has an absolute limit of +/-42 volts at the rails, or so sayeth the data sheet.

6th March 2005, 03:24 AM	#4
DonoMan diyAudio Member Join Date: Feb 2005 Location: Massachusetts	damn, I'm good at confusing lm4780 for other chips I've seen, lol

6th March 2005, 10:06 AM	#6
DonoMan diyAudio Member Join Date: Feb 2005 Location: Massachusetts	It would be +/- 47V max if you have an input (so if you ground the input through a resistor, it may be ok) so says the data sheet, actually (I hadn't realized before that it was for both rails heh) and if your transformer is 35-0-35 then you'd have 49.5V after DC conversion. Options: 1) Try it anyway (bad idea but might be ok with a really big heatsink) 2) Regulate the power supply down to ~40V for voltage (best idea IMO, as regulating has other advantages as well) 3) Modify the transformer 4) Get a new transformer

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