Laplace Transform Formulas & Theory

Reference guide for Laplace transform formulas and theoretical background

Laplace Transform Formulas

Function NameTime Domain f(t)Laplace Transform F(s)Convergence Condition
Constantcc/ss > 0
Power Functiont^nn!/s^(n+1)s > 0, n > -1
Exponential Functione^(at)1/(s-a)s > a
Sine Functionsin(at)a/(s^2+a^2)s > 0
Cosine Functioncos(at)s/(s^2+a^2)s > 0
Hyperbolic Sine Functionsinh(at)a/(s^2-a^2)s > |a|
Hyperbolic Cosine Functioncosh(at)s/(s^2-a^2)s > |a|
Exponentially Decaying Sine Functione^(-at)sin(bt)b/((s+a)^2+b^2)s > -a
Exponentially Decaying Cosine Functione^(-at)cos(bt)(s+a)/((s+a)^2+b^2)s > -a
Step Functionu(t-a)e^(-as)/ss > 0, a > 0
Impulse Functionδ(t-a)e^(-as)a ≥ 0
Ramp Functiont1/s^2s > 0
Quadratic Functiont^22/s^3s > 0
t times Exponential Functiont*e^(at)1/(s-a)^2s > a
t times Sine Functiont*sin(at)2as/((s^2+a^2)^2)s > 0
t times Cosine Functiont*cos(at)s^2-a^2/((s^2+a^2)^2)s > 0

Laplace Transform Theory

What is the Laplace Transform?

The Laplace transform is an integral transform that converts a function of time f(t) to a function of complex frequency s, F(s). The Laplace transform has widespread applications in solving differential equations, analyzing control systems, and signal processing.

Definition of the Laplace Transform

The Laplace transform of a function f(t) is defined as:

F(s) = L{f(t)} = ∫0 e-stf(t)dt

Inverse Laplace Transform

The inverse Laplace transform converts a function F(s) back to the time domain function f(t):

f(t) = L-1{F(s)} = (1/2πi)∫γ-i∞γ+i∞ estF(s)ds

Application Areas

Circuit Analysis

In circuit analysis, Laplace transform is used to convert differential equations in the time domain to algebraic equations in the s-domain, simplifying the analysis process.

Control Systems

In control systems, Laplace transform is used to analyze system stability, response characteristics, and transfer functions.

Signal Processing

In signal processing, Laplace transform is used to analyze the frequency domain characteristics of continuous-time signals.

Differential Equation Solving

Laplace transform is a powerful tool for solving linear constant-coefficient differential equations, especially for non-homogeneous equations and initial value problems.

Mechanical Vibrations

In mechanical vibration analysis, Laplace transform is used to solve for the response of vibrating systems.

Heat Conduction

In heat conduction problems, Laplace transform is used to solve the heat conduction equation.