Ok, thanks for the long and excellent explanation. You made me get off of my duff and walk down to check the part. You are absolutely right and I mis-remembered. The parts I have are 340/78xx. I always wanted to know why they were dual marked but sorry for the mistaken part number.

Can't believe but last night I opened my multi output power supply (built with just 12 fixed output regulators) and the one I needed to check was a 340 also marked 7805. I had forgot the detail after assembling it, probably more than 10 or 15 years ago...

Sure I read datasheets even if I cannot get full benefit from them.

My datasheet (Linears) regulators, opamps, comaprators, ADC /DAC, etc is dated 1982.

 

Being publicly smacked by the guy who actually wrote the datasheet?

Priceless!

To be fair to the OP: there is a reason that the "complicated" information is buried at the back of the data sheet where most people don't get to...... we were forced to do that by Marketing because they didn't want the customers to be "scared" by info that made the part look difficult to use. They also restricted some things from being included and in some cases, we had to take it upstairs to get the info published.

If we had gotten our way, data sheets would have been shorter and less confusing.