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[aprssig] LM7805 and caps

Andrew Rich vk4tec at people.net.au
Sun Aug 26 20:36:50 UTC 2007


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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Andrew Rich VK4TEC
vk4tec at people.net.au
http://www.tech-software.net



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