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BIPOLAR OUTPUT CIRCUIT
V
OUT
+
ǒ
D
32768
*1
Ǔ
V
REF
(2)
D0
R
1
A
R
1
A R
2
A
D15
Parallel
Bus
Interface
InputA
Register
DACA
Register
DACA
Control
Logic
RS
RSTSEL
R
COM
A
V A
REF
R
OFS
A
R
OFS
A R
FB
A
R
FB
A
V
DD
I
OUT
A
AGNDA
DAC8822
OPA2277
U1
OPA2277
V
OUT
C
1
U2
V
REF
DGND
WR
A0
A1
LDAC
DAC8822
SBAS390A – DECEMBER 2006 – REVISED MARCH 2007
APPLICATION INFORMATION (continued)
The DAC8822, as a 4-quadrant multiplying DAC, can be used to generate a bipolar output. The polarity of the
full-scale output (I
OUT
) is the inverse of the input reference voltage at V
REF
.
Using a dual op amp, such as the OPA2277 , full 4-quadrant operation can be achieved with minimal
components. Figure 43 demonstrates a ± 10V
OUT
circuit with a fixed +10V reference. The output voltage is
shown in Equation 2 :
Figure 43. Bipolar Output Circuit for Channel A
17
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