MCP4024 MICROCHIP [Microchip Technology], MCP4024 Datasheet - Page 49

• Manufacturer Part Number: MCP4024
• Manufacturer: MICROCHIP [Microchip Technology]

8.2
Figure
amplifier circuits that could replace fixed resistors with
the MCP4021/2/3/4 to achieve digitally-adjustable
analog solutions.
Figure 8-4 shows a circuit that allows a non-inverting
amplifier to have its’ offset and gain to be independently
trimmed. The MCP4021 is used along with resistors R1
and R2 to set the offset voltage. The sum of R1 + R2
resistance should be significantly greater (> 100 times)
the resistance value of the MCP4021. This allows each
increment or decrement in the MCP4021 to be a fine
adjustment of the offset voltage. The input voltage of
the op amp (V
voltage. The gain is adjusted by the MCP4022. If the
resistance value of the MCP4022 is small compared to
the resistance value of R3, then this is a fine
adjustment of the gain. If the resistance value of the
MCP4022 is equal (or large) compared to the
resistance value of R3, then this is a course adjustment
of the gain. In gerneral, 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
8-3,
1
2
A
B
V
Operational Amplifier
Applications
DD
R
3
Figure 8-4
W
IN
) should be centered at the op amps V
MCP4021
A
W
Trimming Offset and Gain in
and
B
Figure 8-5
Op Amp
–
+
MCP6001
R
illustrate typical
4
V
OUT
W
FIGURE 8-4:
a Non-Inverting Amplifier.
FIGURE 8-5:
Thevenin
Equivalent
R
R
1
2
A
B
V
R
R
DD
1
2
MCP4022
A
B
V
W
DD
R
3
R
W
V
Pot
Eq
IN
Pot
1
V
MCP4021/2/3/4
=
MCP4021
IN
2
A
W
(
R
V
MCP4022
A
1
W
Trimming Offset and Gain in
+
Programmable Filter.
B
R
AB
W
Op Amp
+
–
–
f
R
c
Op Amp
WB
–
+
=
R
V
3
-----------------------------
2
)
DD
π
||
DS21945E-page 49
R
MCP6021
⋅
(
4
R
R
1
Eq
2
MCP6291
+
⋅
R
C
WB
V
V
)
OUT
OUT
+
R
w