Re: 7805 failure mode
- From: "DaveM" <masondg4499@xxxxxxxxxxxxx>
- Date: Tue, 24 Jul 2007 20:32:59 -0400
"Winfield" <winfieldhill@xxxxxxxxx> wrote in message
news:1185277179.616564.238280@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Paul Hovnanian wrote:
Winfield Hill wrote:
[snip]
One possible clue: when the 7805 was first
used in this circuit, a hand-wired prototype,
the ground pin was left floating. But when
the failure mode was observed this pin was
properly grounded.
Some clarification needed: by 'the ground pin' you are
referring to the 7805 common pin, correct?
Yes.
When the pin was properly grounded, did the 7805 resume normal
operation? If so, I wouldn't call what you experienced
a 'failure'. It would be 'unspecified behaviour'.
It operates normally, except for the short turn-on
voltage spike every time the power is applied.
Wonder what happens if you were to drive the common pin with a low impedance
square wave source? Do you see the spikes on the edges of the square wave?
How wide are the spikes?
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)
"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra
.
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- From: Winfield Hill
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