Stability from laplace transform analysis

All,

Can any one pls explain me how "sigma" in s in laplace transform > 0 means
un-stable system and < 0 means stable system?

My understanding is completely reverse to that.

BR,
Dhaval

On 13 Jan, 13:52, "dhaval_shah" <shah.dhavals...@gmail.com> wrote:
> All,
>
> Can any one pls explain me how "sigma" in s in laplace transform > 0 means
> un-stable system and < 0 means stable system?
>
> My understanding is completely reverse to that.

The Laplace Transform contains an exponential term exp(+/-s)
where

s = sigma + jw.

Depending on the choise of sign in that exponent, the sigma
term corresponds to a time domain term that either grows
or decays exponentially with increasing time.

The *conventional* *choise* of signs is such that sigma < 0
corresponds to an exponentially decaying term in time domain.

Rune