
18-16 Electrical Variables
e circuit section aer node 4 is a low-pass lter that extracts the dc component of the input signal.
e
refore,
t
he
c
ircuit
o
utput
v
oltage
i
s
g
iven
b
y
V
k
T
v t t kV
T
o i
2
i
2
0
d= =
∫
( )
(18.44)
thus providing an output signal proportional to the squared rms value of the input signal v
i
(t) in accor-
dance
wi
th
Eq
uation
18.40. Qu
antities
k
1
, k
2
, and k depend on the values of the elements in the circuit in
Fi
gure
18.14. Un
der
ci
rcuit
op
erating
co
nditions,
th
eir
va
lues
ca
n
be co
nsidered
co
nstant,
so th
at
k
1
, k
2
,
an
d
k c
an
b
e
c
onsidered
c
onstant
a
lso
.
If ca
refully
de
signed,
th
is
ci
rcuit
ca
n
fe
ature
an un
certainty
in th
e
ra
nge
of ...