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8255
(
PORT A J
(PA0-7)
1
(
PoRT c r
L O W E R 1
( P A o . 3 )
[
PORT C T
l'l^::;
1
Fig. 1-16 - Adding puil-ups and putt_downs
to Digitat t/O Lines
Resistor Configurable Gain
Thel200 has resitor configurable gain
b c11om1ze. the gain sening for a
-lpecific apprication. Note that when
i:l,Hr[[ H#:,T,fr:"
up the boaio ror a gain or on.ifi-'ffi;r
,n" ro input .r,i,inrri w'r operate
onry at
The resisror configurable gain is derived
by adding resislors Rl and-R2, trimpot
TR4, and capacibr c36, all
located in the upper tt'"* -o'tiehi;;'#,i;
board:The;e;i;r^ -o trimpotiombin"
to ,"t rhe gain, as shown
in the formula in Figure 1-17' ca;;ilor
cii i. p-"lo"a ,o n"iv"" Jrr
"oo
low-pass filrering in the gain circuit.
If
your input signal is a slowly crranging
one ;;;""
do nor need ,;;;;*
it at a.higher B@, you may wanr
to add a
capacitor at c36 in order ,oredu": n""
itp* il;qu€ncy range and in turn reduce
ttre noise on'your input signar. The
formula for setting the frequencv is given
in ttre oiagram. Hg* i-rirn"*,
lJ;;;;l#itry
is configured.
As shown in Figure 1'77 ' asolder short
must be removed from trre board to
activate the gain circuiry. This
::l#:ffled
on the bottom side of ne boarJ uno errJ7r
a'D;i;ic1. rig* l-18 shows rie rocation or *re
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