Datasheet
© 2011 Microchip Technology Inc. DS25073A-page 33
MCP6N11
4.4 Typical Applications
4.4.1 HIGH INPUT IMPEDANCE
DIFFERENCE AMPLIFIER
Figure 4-11 shows the MCP6N11 used as a difference
amplifier. The inputs are high impedance and give good
CMRR performance.
FIGURE 4-11: Difference Amplifier.
4.4.2 DIFFERENCE AMPLIFIER FOR
VERY LARGE COMMON MODE
SIGNALS
Figure 4-12 shows the MCP6N11 INA used as a
difference amplifier for signals with a very large
common mode component. The input resistor dividers
(R
1
and R
2
) ensure that the voltages at the INA’s inputs
are within their range of normal operation. The
capacitors C
1
, with the parasitic capacitances C
2
(the
resistors’ parasitic capacitance plus the INA’s input
common mode capacitance, C
CM
), set the same
division ratio, so that high-frequency signals (e.g., a
step in voltage) have the same gain. Select the INA
gain to compensate for R
1
and R
2
’s attenuation. Select
R
1
and R
2
’s tolerances for good CMRR.
FIGURE 4-12: Difference Amplifier with
Very Large Common Mode Component.
4.4.3 HIGH SIDE CURRENT DETECTOR
Figure 4-13 shows the MCP6N11 INA used as to detect
and amplify the high side current in a battery powered
design. The INA gain is set at 21 V/V, so V
OUT
changes
210 mV for every 1 mA of I
DD
current. The best G
MIN
option to pick would be a gain of 10 (MCP6N11-010).
FIGURE 4-13: High Side Current Detector.
4.4.4 WHEATSTONE BRIDGE
Figure 4-14 shows the MCP6N11 single
instrumentation amp used to condition the signal from
a Wheatstone bridge (e.g., strain gage). The overall
INA gain is set at 201 V/V. The best G
MIN
option to pick,
for this gain, is 100 V/V (MCP6N11-100).
FIGURE 4-14: Wheatstone Bridge
Amplifier.
V
OUT
V
IP
V
DD
V
IM
V
REF
V
FG
R
F
R
G
U
1
MCP6N11
V
OUT
V
DD
V
REF
V
FG
R
F
R
G
R
2
R
1
V
2
C
1
C
2
R
2
R
1
V
1
C
1
C
2
U
1
MCP6N11
I
DD
=
(V
BAT
–V
DD
)
(10
Ω
)
=
(V
OUT
–V
REF
)
(10
Ω
) (21.0 V/V)
10 Ω
V
DD
I
DD
V
BAT
+1.8V
to
+5.5V
V
OUT
V
REF
V
FG
R
F
R
G
200 kΩ
10 kΩ
U
1
MCP6N11
V
OUT
V
REF
V
FG
R
F
R
G
200 kΩ
1kΩ
V
DD
R
W1
R
W2
R
W2
R
W1
U
1
MCP6N11