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Old 12th September 2011, 02:48 PM   #1
syklab is offline syklab  Hong Kong
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Default LM723 Voltage regulator

Hi,
Anyone have experience in using this regulator ? How is it compare to the mainstream 317 type?

Thanks
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Old 12th September 2011, 04:09 PM   #2
RJM1 is offline RJM1  United States
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Not since the early 80’s when I was fixing b+w vidicon security cameras.
I’m not sure when they first came out but they are in my February 1973
Edition of the “Fairchild Semiconductor Linear Circuits Catalog”.
Although the patent for the Lm317 was in 1971.
US patent 3617859
Not much has changed in 40 years.
Te Lm317 requires fewer external parts and is easier to use.
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Old 6th September 2012, 04:42 PM   #3
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They appear to be extremely versatile regulators.
http://www.ti.com/lit/ds/symlink/lm723.pdf
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Old 6th September 2012, 04:48 PM   #4
Tajzmaj is offline Tajzmaj  Slovenia
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Nice one. It is running in my workbench psu. But don't supply it more than 32-33V otherwise it is quite easy to kill it. Of course you will need some external power transistors to get more than few mA from it.
Cheers, Taj
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Old 6th September 2012, 04:54 PM   #5
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The data sheet says it's good for 150mA. I like the fact that you can use it for both positive and negative supplies. I'm interested in trying it.
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Old 6th September 2012, 05:01 PM   #6
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It can be used for positive and negative supplies: that is only partly true. There is no true negative version. Any positive 3 pin reg can also be used for negative supplies by using it to GND....

LM723 can put out 150 mA but not at 5 V out and 30 V in to give an example. It is way better than LM317 but that should be clear just from looking at the specs. It is also less easy to implement and requires external parts and thus extra board space. Features that don't give a warm feeling to designers.

You know what wins: the part that is cheapest, not the part that is best.
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Last edited by jean-paul; 6th September 2012 at 05:03 PM.
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Old 6th September 2012, 05:05 PM   #7
Tajzmaj is offline Tajzmaj  Slovenia
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Problem is it's small max dissipation. It comes in dip14 enclosure which means probably some 0.5W. I'm just guessing but it is probably close. With only one output transisttor you can easily reach quite high currents. In my case I drive one MJ11015 (I think this one is npn) TO3 darlington...
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Old 6th September 2012, 05:07 PM   #8
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Compared with modern SMD LDO regs 0.66 W (see data sheet) is not a bad figure at all Just like the 40 V max. input voltage and eh ... the noise figures.
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Last edited by jean-paul; 6th September 2012 at 05:10 PM.
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Old 6th September 2012, 05:14 PM   #9
Tajzmaj is offline Tajzmaj  Slovenia
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Jean-Paul..hehe
You are right. 0.5W is quite decent, but for diy where the best solution is the cheapest one it might be a little too low. We all tend to use some old transformer with not very ideal secondary voltages which results in high dissipations in most cases.
And I can't agree more. 317 is cheap and easy to work with. If you don't need current regulation and such things than 723 might be too complicated.
Best regards
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Old 6th September 2012, 05:19 PM   #10
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New Breed of Ultra Low Noise Regulators H i F i D U I N O
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