Data Sheet

© 2009 Microchip Technology Inc. DS22039D-page 37
MCP4725
8.5.4 BIPOLAR OPERATION
Bipolar operation is achievable using the MCP4725 by
using an external operational amplifier (op amp). This
allows a general purpose DAC, with its cost and
availability advantages, to meet almost any desired
output voltage range, power and noise performance.
Example 8-3 illustrates a simple bipolar voltage source
configuration. R
1
and R
2
allow the gain to be selected,
while R
3
and R
4
shift the DAC's output to a selected
offset. Note that R
4
can be tied to V
DD
(= V
REF
) instead
of V
SS
, if a higher offset is desired. Note that a pull-up
to V
DD
could be used, instead of R
4
, if a higher offset is
desired.
EXAMPLE 8-3: Digitally-Controlled Bipolar Voltage Source.
V
DD
V
OUT
R
3
R
4
R
2
R
1
V
IN
+
0.1 µF
V
CC
+
V
CC
–
V
IN+
V
OUT
R
4
R
3
R
4
+
--------------------=
V
O
V
O
V
IN+
1
R
2
R
1
------+
⎝⎠
⎛⎞
V
DD
R
2
R
1
------
⎝⎠
⎛⎞
–=
To MC U
(MASTER)
R
R
MCP4725
V
DD
V
OUT
A0
SCL
V
SS
1
2
3
4
5
6
V
DD
SDA
10 µF0.1 µF
V
DD
Where: Dn = DAC Input Code (0 – 4095)
V
OUT
V
DD
Dn
2
12
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×=