
8-16 Sensors and Sensor Technology
Figure 8.21 shows the Gm–C lter structure used in this design. e dierential structure has been
used to cancel common mode signals in the signal path.
No
rmally,
th
e
Gm of th
e
Gm–C l
ters
is tu
ned
to ge
t
th
e
pr
oper
cu
to
fr
equency,
bu
t
in th
is
ci
rcuit,
no ex
tra
tu
ning
is ne
cessary,
be
cause
th
e
co
rner
fr
equency
is we
ll
be
low
1 kH
z
. e dc ou
tput
sig
nal
of
th
is
s
tage
g
oes
to t
he
a
nalog-to-digital
c
onverter
s
ection
.
8.3.8 Analog-to-Digital Conversion
Among dierent techniques used for analog-to-digital conversion, sigma–delta is very attractive espe-
cially for low-frequency conversion. Other A/D conversion tech ...