www.德州仪器.com
产品 预告(展)
V
输出
R
FB
C
1
I
OUT1
0
≤
V
输出
≤
+2.5v
地
地
−
2.5v
V
输出
V
在
V
REF
+2.5v 涉及
V
DD
V
DD
DAC7811
OPA277
OPA277
I
OUT2
BipolarOutputSection
V
输出
D
0.5
2
N
1
V
REF
(2)
I
OUT1
R
FB
C
1
地
V
DD
V
DD
+2.5v
(+10v)
V
REF
V
输出
C
2
U4
OPA277
10k
Ω
10k
Ω
5k
Ω
−
2.5v
≤
V
输出
≤
+2.5v
(
−
10V
≤
V
输出
≤
+10v)
U2
OPA277
DAC7811
I
OUT2
ProgrammableCurrentSourceCircuit
I
L
R2
R3
R1
R3
V
REF
D
(3)
DAC7811
SBAS337–APRIL2005
applicationinformation(持续)
figure30.positivevoltageoutputcircuit
thedac7811,asa2-quadrantmultiplyingdac,canbeusedtogenerateaunipolaroutput.thepolarityofthe
全部-scaleoutputi
输出
istheinverseoftheinputreferencevoltageatV
REF
.
someapplicationsrequirefull4-quadrantmultiplyingcapabilitiesorbipolaroutputswing.asshowninfigure31,
externalopampu4isaddedasasummingampandhasagainof2xthatwidenstheoutputspanto5v.一个
4-quadrantmultiplyingcircuitisimplementedbyusinga2.5voffsetofthereferencevoltagetobiasu4.
accordingtothecircuittransferequationgiveninequation2,inputdata(d)fromcode0tofull-scaleproduces
outputvoltagesofV
输出
=–2.5vtov
输出
=+2.5v.
externalresistancemismatchingisthesignificanterrorinfigure31.
figure31.bipolaroutputcircuit
ADAC7811canbeintegratedintothecircuitinFigure32toimplementanimprovedHowlandcurrentpumpfor
precisevoltagetocurrentconversions.bidirectionalcurrentflowandhighvoltagecompliancearetwofeaturesof
thecircuit.withamatchedresistornetwork,theloadcurrentofthecircuitisshownbyequation3:
13