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Is it possible to connect 3 LM317s in parallel to get upto 4A of current output ? I need 4A but I'm not able to figure out any other possibility. Is there any other possibility to achieve this ?

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    \$\begingroup\$ You might even want to read the datasheet. There's an example in it for getting high current with regulated voltage. \$\endgroup\$
    – JRE
    Apr 6 '16 at 17:16
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    \$\begingroup\$ @JRE, you might want to specify which LM317 datasheet. Not all of them have the same application circuits. \$\endgroup\$
    – The Photon
    Apr 6 '16 at 17:18
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    \$\begingroup\$ OP, TI's LM317 datasheet has an application circuit specifically for 4 A output, in figure 23. \$\endgroup\$
    – The Photon
    Apr 6 '16 at 17:22
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    \$\begingroup\$ Yes it possible. But is it a good idea ? No For this much current, just don't use LM317 or any other linear regulator. Switched converters have been developed, they come on cheap modules, cheaper than the heatsinks you need for all those LM317s anyway. \$\endgroup\$ Apr 6 '16 at 17:28
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    \$\begingroup\$ Use lm338 it's like lm317 ,but deliver 5amp \$\endgroup\$
    – Ragesh
    Sep 12 '17 at 2:13
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Yes, it is possible. Do not connect the outputs directly together but rather put a small resistor (0.5 Ohm or so) between each output and the summing node.

Check: http://www.ti.com/lit/ds/symlink/lm317.pdf 8.3.11 Adjustable 4-A Regulator Circuit on page 15/16.

You can also look at 9.3.13 which generates higher current with a single LM317, using instead NPN's to deliver the extra current.

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  • \$\begingroup\$ You meant 8.3.12 on page 17, didn't you? \$\endgroup\$ Sep 12 '17 at 4:52
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You really need a switcher solution. TI/National has chips that will do what you want and software to make the design a snap. I've used them.

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  • \$\begingroup\$ Examples (ICs) and references (datasheets and their application circuits) are appreciated. \$\endgroup\$ Sep 12 '17 at 4:54
  • \$\begingroup\$ This is correct. Linear regulators at the 4A level should be few and far between. \$\endgroup\$ May 4 '18 at 15:22

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