
33-16 Electrical Variables
33.25 FET Noise Model
Figure 33.4a shows the MOSFET noise equivalent circuit, where i
td
is the channel thermal noise current
an
d
i
fd
is the channel icker noise current [1–7]. e mean-square values of these currents are given by
i
kT f
g
td
m
2
8
3
=
∆
(3
3
.67
)
i
K f
Kf L C
fd
f
ox
2
2
4
=
(3
3
.68
)
where
K
i
s
t
he
t
ransconductance
p
arameter
g KI
= 2
is the transconductance
L
i
s
t
he
e
ective
l
ength
o
f
t
he
c
hannel
C
ox
is the gate oxide capacitance per unit area
Let
th
e
re
sistances
to sig
nal
gr
ound
se
en
lo
oking
ou
t
of th
e
ga
te
an
d
th
e
so
urce,
re
spectively,
be de
noted
by R
1
and R
2
. e mean-square equivalent noise input voltage in series with either ...