Electronics > Beginners
Lm317 vs LM338
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Mr. Scram:

--- Quote from: Audioguru again on August 25, 2019, 08:14:03 pm ---Nope. The minimum load for the more expensive LM138 is 5mA when the input voltage is fairly high. For the LM338 it is 10mA. Therefore the value of the output to adj resistor is too high. Use 120 ohms and change the pot to match.
But it affect only the output voltage rising with no load and will not cause the IC to short.

Why do people buy cheap Chinese fakes anyway??

--- End quote ---
Probably for the same reason we don’t all have a lab filled with R&S and Keithley gear.
exe:

--- Quote from: queennikki1972 on August 25, 2019, 08:23:43 pm ---Because not everyone can afford $0.25 resistors.

--- End quote ---

A fake component can cause a lot of damage, consume a lot of time to troubleshoot, and cannot guarantee performance. For these reasons I suggest not to buy ICs from unauthorized suppliers.

I do buy things from China when I can verify performance, or I'm willing to take the risk, or just for fun, or I believe the part is hard to fake, or when a part is not available elsewhere.
floobydust:
I used to use Linear Tech version LT138A/338A which was in a beefy package TO-3 or TO-3P. That thing was tough and had higher SOA output current.  But too bad it's obsolete now.
Audioguru again:
A real LM338 will shut down safely if it is overloaded and gets too hot. A fake one might simply melt into a short circuit.
EDIT: An LM338 at Digikey costs less than a cheap McDonalds hamburger.
Mr. Scram:

--- Quote from: Audioguru again on August 26, 2019, 03:10:53 am ---A real LM338 will shut down safely if it is overloaded and gets too hot. A fake one might simply melt into a short circuit.
EDIT: An LM338 at Digikey costs less than a cheap McDonalds hamburger.

--- End quote ---
If you include shipping the difference can be 1000%
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