Laplace Transform

Laplace transforms are an adapted integral form of a differential equation (created and introduced by the French mathematician Pierre-Simon Laplace (1749-1827)) used to describe electrical circuits and physical processes. Adapted from previous notions given by other notable mathematicians and engineers like Joseph-Louis Lagrange (1736-1812) and Leonhard Euler (1707-1783), Laplace transforms are used to be a more efficient and easy-to-recognize form of a mathematical equation.

Standard Form

This is the standard form of a Laplace transform that a function will undergo.

F(s)={\mathcal {L}}\left\{f(t)\right\}=\int _{0}^{\infty }e^{-st}f(t)\,dt

Sample Functions

The following is a list of commonly seen functions of which the Laplace transform is taken. The start function is noted within the Laplace symbol ${\mathcal {L}}\left\{\right\}$ .

F(s)={\mathcal {L}}\left\{1\right\}=\int _{0}^{\infty }e^{-st}\,dt=

{\frac {1}{s}}

F(s)={\mathcal {L}}\left\{t^{n}\right\}=\int _{0}^{\infty }e^{-st}t^{n}\,dt=

{\frac {n!}{s^{n+1}}}

F(s)={\mathcal {L}}\left\{e^{at}\right\}=\int _{0}^{\infty }e^{-st}e^{at}\,dt=

{\frac {1}{s-a}}

F(s)={\mathcal {L}}\left\{sin(\omega t)\right\}=\int _{0}^{\infty }e^{-st}sin(\omega t)\,dt=

{\frac {\omega }{s^{2}+\omega ^{2}}}

F(s)={\mathcal {L}}\left\{cos(\omega t)\right\}=\int _{0}^{\infty }e^{-st}cos(\omega t)\,dt=

{\frac {s}{s^{2}+\omega ^{2}}}

F(s)={\mathcal {L}}\left\{t^{n}g(t)\right\}=\int _{0}^{\infty }e^{-st}t^{n}g(t)\,dt=

{\frac {(-1)^{n}d^{n}G(s)}{ds^{n}}}{\mbox{ for}}~n\ {\mbox{= 1,2,...}}

F(s)={\mathcal {L}}\left\{tsin(\omega t)\right\}=\int _{0}^{\infty }e^{-st}tsin(\omega t)\,dt=

{\frac {2\omega s}{(s^{2}+\omega ^{2})^{2}}}

F(s)={\mathcal {L}}\left\{tcos(\omega t)\right\}=\int _{0}^{\infty }e^{-st}tcos(\omega t)\,dt=

{\frac {s^{2}-\omega ^{2}}{(s^{2}+\omega ^{2})^{2}}}

F(s)={\mathcal {L}}\left\{g(at)\right\}=\int _{0}^{\infty }e^{-st}g(at)\,dt=

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F(s)={\mathcal {L}}\left\{e^{at}g(t)\right\}=\int _{0}^{\infty }e^{-st}e^{at}g(t)\,dt=G(s-a)

F(s)={\mathcal {L}}\left\{e^{at}t^{n}\right\}=\int _{0}^{\infty }e^{-st}e^{at}t^{n}\,dt=

{\frac {n!}{(s-a)^{n+1}}}{\mbox{ for}}~n\ {\mbox{= 1,2,...}}

F(s)={\mathcal {L}}\left\{te^{-t}\right\}=\int _{0}^{\infty }e^{-st}te^{-t}\,dt=

{\frac {1}{(s+1)^{2}}}

F(s)={\mathcal {L}}\left\{1-e^{-t/T}\right\}=\int _{0}^{\infty }e^{-st}(1-e^{-t/T})\,dt=

{\frac {1}{s(1+Ts)}}

F(s)={\mathcal {L}}\left\{e^{at}sin(\omega t)\right\}=\int _{0}^{\infty }e^{-st}e^{at}sin(\omega t)\,dt=

{\frac {\omega }{(s-a)^{2}+\omega ^{2}}}

F(s)={\mathcal {L}}\left\{e^{at}cos(\omega t)\right\}=\int _{0}^{\infty }e^{-st}e^{at}cos(\omega t)\,dt=

{\frac {s-a}{(s-a)^{2}+\omega ^{2}}}

F(s)={\mathcal {L}}\left\{u(t)\right\}=\int _{0}^{\infty }e^{-st}u(t)\,dt=

{\frac {1}{s}}

F(s)={\mathcal {L}}\left\{u(t-a)\right\}=\int _{0}^{\infty }e^{-st}u(t-a)\,dt=

{\frac {e^{-as}}{s}}

F(s)={\mathcal {L}}\left\{u(t-a)g(t-a)\right\}=\int _{0}^{\infty }e^{-st}u(t-a)g(t-a)\,dt=e^{-as}G(s)

F(s)={\mathcal {L}}\left\{g'(t)\right\}=\int _{0}^{\infty }e^{-st}g'(t)\,dt=sG(s)-g(0)

F(s)={\mathcal {L}}\left\{g''(t)\right\}=\int _{0}^{\infty }e^{-st}g''(t)\,dt=s^{2}\cdot G(s)-s\cdot g(0)-g'(0)

F(s)={\mathcal {L}}\left\{g^{(n)}(t)\right\}=\int _{0}^{\infty }e^{-st}g^{(n)}(t)\,dt=s^{n}\cdot G(s)-s^{n-1}\cdot g(0)-s^{n-2}\cdot g'(0)-...-g^{(n-1)}(0)

Transfer Function

The Laplace transform of the impulse response of a circuit with no initial conditions is called the transfer function. If a single-input, single-output circuit has no internal stored energy and all the independent internal sources are zero, the transfer function is