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Quick question about voltage regulator?

For a 5v voltage regulator should I buy the LM7805ACT which has 3A 2% OUTPUT TOL 3-TERMINAL or the LM7805SCT which has 1A Pos Vol Reg? The second is slightly more expensive, but they appear to be pretty similar so I'm not really sure what the difference is.

I'm using it to regulate a 9v power source to an axe023 by the way. 



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According to the datasheet from Octopart, the LM7805ACT has an output limit of 1A, not 3A. I couldn't find much info on the 'SCT model, so my guess is that it's an obsolete part. Go with the 'ACT would be my suggestion.

I don't know the SCT parts either, but the AC 7400 series is a medium speed chip. They are faster than the obsolete S (Schottky) chips, but slower than the F (Fast) chips. The "T" at the end of both ACT and SCT should mean the logic levels are compatible with both TTL and CMOS (3.3 V) logic.  Speed shouldn't be very important if you are regulating voltage from a battery.

Before you buy either, I recommend you read the excellent Tip/Walkthrough by OddBot on voltage regulation.


A low dropout regulator like the LM2940CT-05 or 278RA05C may be better choices, depending on your application. They will continue to regulate the voltage even when it gets to like 0.5V above your desired output.

Great, thanks, I'm buying it. :)