[OZAPRS] LM7805 and caps

[Hamish Moffatt]

On Mon, Aug 27, 2007 at 06:36:50AM +1000, Andrew Rich wrote:
> Can someone explain to me why this is so:
> 
> I have been building some projects now that use LM7805 voltage
regulators.
> 
> This is now the second time I have had issues with a PIC chip not
running.
> 
> It is only when I add caps to the input and the output that it settles
down.
> 
> Looking on the CRO, the DC looked noisy.
> 
> I thought that the caps where there to trap AC.
> 
> Do caps on an LM7805 player a larger role ? Is there something inside
the
> reg that needs external C ?

I could've sworn there was a QST article featuring a transmitter for 80m
or so that used a 78xx as the main oscillator.

They oscillate especially if there is a bit of track length between them
and their input. I have had one explode. I usually solder caps directly
across the pins now.

Hamish
-- 
Hamish Moffatt VK3SB <hamish at debian.org> <hamish at cloud.net.au>
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