On Wed, 15 Dec 2004, John J. McDonough wrote:

> ----- Original Message -----
> From: "Jinx" <joecolquitt@clear.net.nz>
> Subject: Re: [PIC] First PIC based circuit
>
>> A diode, eg 1N4001, from the output (anode) of the 7805 to the
>> input (cathode) is recommended with such a large o/p cap. If the
>> input is shorted to ground for some reason the 7805 will die because
>> its o/p V is higher than its i/p
>
> Is it even possible to kill a 7805?  I've run them into a dead short and got
> some nasty burns to show for it, but the 7805 merrily kept trying to drive
> ground to 5 volts.  But watch out, they can get amazingly hot!

You can kill an old 7805 like this, and a clone 7805. New 7805s of good 
make have SOA limiting and shut down when they get too hot.

Peter
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