MCP4012 Microchip Technology Inc., MCP4012 Datasheet - Page 45

• Manufacturer Part Number: MCP4012
• Description: Low-cost 64-step Volatile Digital Pot
• Manufacturer: Microchip Technology Inc.

8.2
Figure
amplifier circuits that could replace fixed resistors with
the MCP4011/2/3/4 to achieve digitally-adjustable
analog solutions.
Figure 8-4
amplifier to have its’ offset and gain to be independently
trimmed. The MCP4011 is used along with resistors R
and R
resistance should be significantly greater (> 100 times)
the resistance value of the MCP4011. This allows each
increment or decrement in the MCP4011 to be a fine
adjustment of the offset voltage. The input voltage of
the op amp (V
voltage. The gain is adjusted by the MCP4012. If the
resistance value of the MCP4012 is small compared to
the resistance value of R
of the gain. If the resistance value of the MCP4012 is
equal (or large) compared to the resistance value of R
then this is a course adjustment of the gain. In general,
trim the course adjustments first and then trim the fine
adjustments.
FIGURE 8-3:
an Inverting Amplifier.
© 2006 Microchip Technology Inc.
V
IN
R
R
2
8-3,
1
2
to set the offset voltage. The sum of R
A
B
V
Operational Amplifier
Applications
DD
R
shows a circuit that allows a non-inverting
3
Figure 8-4
W
IN
) should be centered at the op amps V
MCP4011
A
W
Trimming Offset and Gain in
and
3
B
, then this is a fine adjustment
Figure 8-5
Op Amp
–
+
MCP6001
R
illustrate typical
4
1
V
+ R
OUT
3
w
1
2
,
FIGURE 8-4:
a Non-Inverting Amplifier.
FIGURE 8-5:
Thevenin
Equivalent
R
R
1
2
A
B
V
R
R
DD
1
2
MCP4011
A
B
V
W
DD
R
3
R
W
V
Pot
Eq
IN
Pot
V
1
MCP4011/2/3/4
=
MCP4011
IN
2
A
W
(
R
V
A
MCP4012
1
W
Trimming Offset and Gain in
+
Programmable Filter.
B
R
AB
W
Op Amp
+
–
–
f
R
c
Op Amp
WB
V
–
+
=
R
DD
3
-----------------------------
2
)
π
||
DS21978C-page 45
R
MCP6021
⋅
(
4
R
R
MCP6291
1
Eq
2
+
⋅
R
C
WB
V
V
)
OUT
OUT
+
R
w