20mV? Where do you get your 7805s? I’ve never seen one that good!

 

20mV? Where do you get your 7805s? I’ve never seen one that good!

OK, 25 millivolts. Look at the portion of the spec sheet shown in post #16.
The reality is that now there are a lot of companies producing LM7805 regulators and many of them are not as good as the original specs describe.
AND, once again, it is important to bypass the input to the IC as well as the output.

 

250mV more like! TI’s spec is 4.75V to 5.25V (coincidentally, the same as 7400 TTL).
Agreed on input bypass.
I’d also add the aluminium electrolytic on the output like Mr. Pease says.

Worth noting that the 5mA load for guaranteed output voltage applies to the 7805. It’s 1mA for the 78L05, so worth using the little one for low current supplies. Also worth noting that the LP2951 is more accurate (+/- 1% for load>100μA). It costs more, but in the long run it could save you from having to buy a voltage reference.

 

it is important to bypass the input to the IC as well as the output.

hi MB2,
I agree, else you can get instability.
E

 

I seem to of opened a can of worms here. I just remember building circuits where the voltage regulators didn't regulate properly until there was a load on them. They were probably LM317's, due to the versatility of easy voltage adjustment. Still, it's good to get a debate going.

 

hi MB2,
I agree, else you can get instability.
E

Not merely "instability, if there is a bit of resistance you can get some serious oscillation around 20 MHz. Been there done that!