
223
Frequency Domain
7.1 INTRODUCTION
We saw in Section 4.6 of Chapter 4 that the equations for voltage and current for
capacitors are
)
(
=it C
dv t
;
1
0
∫
() ()
vt
itdt v
and in Section 4.6 for inductors
()
=vt L
di t
;
1
∫
() ()
it
vtdt i
Such equations depend on time, which is the domain of our functions.
However, thanks to a mathematical tool, an integral transform, it is possible
to change the domain of functions and operate not in time but in frequency or,
more generically, in the domain of the complex argument s by the Laplace trans-
form, denoted
Lft
. In such a way, the equations of capacitors and inductors
are no longer given by derivat ...