
33-21Noise Measurement
measured mean-square noise voltage with the circuit under test driving the amplier. e dierence is the
me
an-square
no
ise
du
e
to th
e
ci
rcuit
. Id
eally,
th
e
am
plier
sh
ould
ha
ve
no e
ect
on th
e
me
asured
no
ise
.
e no
ise
vo
ltage
ov
er
a ba
nd
ca
n
be me
asured
wi
th
ei
ther
a sp
ectrum
ana
lyzer
or wi
th
a l
ter
ha
ving
a kn
own
no
ise
ba
ndwidth
an
d
a vo
ltmeter
. e no
ise
ca
n
be re
ferred
to th
e
in
put
of th
e
ci
rcuit
un
der
te
st
by di
viding
by th
e
to
tal
ga
in
be
tween
it
s
in
put
an
d
th
e
me
asuring
de
vice
. e me
asuring
vo
ltmeter
sho
uld
ha
ve
a ba
ndwidth
th
at
is at le
ast
10 ti
mes
th
e
no
ise
ba
ndwidth
of th
e
l
ter
. e vo
ltmeter crest factor
is
th