Just use an 47 ohm resistor. It is close enough, then the Tolerance should help out too.

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MechTronics

World of Warcraft is a disease

 

Thank you very much. My teacher has approved the circuit diagram and now I will implement it.

 

I guess you are in Pakistan

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Khizer Naeem Mughal
IIUI

 

Exactly Sir! I am from Rawalpindi, Pakistan. One more question sir. Which one among LM338K and LM340 would be better to implement this 2A dc current source project and why?

 

Krumlink, you should add a smiley when you're joking. I'm afraid our OP took your advice seriously.

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Ron (aka Rube)

 

You need to do some of your homework yourself. Draw schematics of 2 amp regulators using both parts, and calculate the power dissipation of the required resistor. You should be able to deduce the answers to your questions from these calculations.

__________________
Ron (aka Rube)

 

This may or may not be of interest:

http://web.archive.org/web/200611282...fo/d-pscc.html

it is a really simple adjustable 5a constant current power supply.

I've built a few for bench testing high power leds. The one I use the most is based on National's LM1084 ldo regulator, and I have the peak current limited to about 1.1a using a pair of 2.2ohm resistors in series.

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Sir please tell me about it (LM338K or LM340 and why?). Even if power dissipation is the only factor then which one will be better. And also if there is any other factor.

 

I think if you consider the power dissipation in mind ,LM338K is the one best for you.

Other factors depends upon the application in which you wanna use it.

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Khizer Naeem Mughal
IIUI

 

I think if I asked my lecturer for approval of a circuit diagram just two days before the finished article was due to be handed in, he'd laugh openly at me and tell me to come back next year!

Good luck with your project, I hope it works out

Brian

 

For a given supply voltage, the 338 will have higher voltage compliance on the output than the 340. In other words, the 338 can handle a higher resistance load than the 340.

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Ron (aka Rube)

 

2 Days was the time for finalizing the circuit and get it approved by the teacher. Implementation was to be started after that.