[OZAPRS] LM7805 and caps

[Norm VK3XCI]

Why is it so?

In fact I think you'll find the regulator is "taking off", it's a common 
problem. You have to decouple at the regulator and at the PIC if it is 
more than a few cm of pcb track away. usually with a electrolytic/tant 
as well as a ceramic.


Its
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 ?
> 
> Curious
> 
> 
> 
>
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-- 
Norm, VK3XCI,
Mildura, The Wintersun City
QF15bt

Victoria, Australia.
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