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[aprssig] LM7805 and caps

Glenn Little WB4UIV glennmaillist at bellsouth.net
Sun Aug 26 21:58:05 UTC 2007


National Semiconductor invented the three terminal regulator many years ago.

See <http://www.national.com/ds/LM/LM340.pdf#page=8> for a data sheet on 
their current product.

It is always good to follow the design rules set down by the maker of a device.

73
Glenn
WB4UIV



At 03:36 PM 08/26/07, 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
>
>
>
>----------------------------------------------------------------------------
>Andrew Rich VK4TEC
><mailto:vk4tec at people.net.au>vk4tec at people.net.au
>http://www.tech-software.net
>
>
>
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