Datasheet

AD8271
Rev. 0 | Page 16 of 20
APPLICATIONS INFORMATION
The resistors and connections provided on the AD8271 offer
abundant versatility through the variety of configurations that
are possible.
DIFFERENCE AMPLIFIER CONFIGURATIONS
The AD8271 can be placed in difference amplifier configurations
with gains of ½, 1, and 2. Figure 45 through Figure 47 show
sample difference amplifier configurations referenced to ground.
=
07363-053
1
7
10kΩ
AD8271
10kΩ
10kΩ
10kΩ
20kΩ
20kΩ
10kΩ
P4
P3
P2
P1
+IN
GND OUT
OUT
N1
N2
N3
10
9
8
2
3
4
–IN
–IN
+IN
5kΩ
5kΩ
10kΩ
10kΩ
GND
Figure 45. Gain = ½ Difference Amplifier, Referenced to Ground
=
–IN
+IN
10kΩ
10kΩ
10kΩ
10kΩ
GND
07363-054
1
7
10kΩ
AD8271
10kΩ
10kΩ
10kΩ
20kΩ
20kΩ
10kΩ
P4
P3
P2
P1
+IN
NC NC
GND
OUT
OUT
N1
N2
N3
10
9
8
2
3
4
–IN
Figure 46. Gain = 1 Difference Amplifier, Referenced to Ground
=
–IN
+IN
10kΩ
5kΩ
5kΩ
10kΩ
GND
07363-055
1
7
10kΩ
AD8271
10kΩ
10kΩ
10kΩ
20kΩ
20kΩ
10kΩ
P4
P3
P2
P1
OUT
OUT
N1
N2
N3
10
9
8
2
3
4
–IN
GND
+IN
OUT
Figure 47. Gain = 2 Difference Amplifier, Referenced to Ground
The AD8271 can also be referred to a combination of reference
voltages. For example, the reference can be set at 2.5 V, using
just 5 V and GND. Some of the possible configurations are
shown in Figure 48 through Figure 50. Note that the output
is not internally tied to a feedback path, so any of the 10 k
resistors on the inverting input can be used in the feedback
network. This flexibility allows for more efficient board lay-
out options.
+V
S
+ –V
S
2
–IN
=
+IN
5kΩ
5kΩ
10kΩ
10kΩ
07363-056
1
7
10kΩ
AD8271
10kΩ
10kΩ
10kΩ
20kΩ
20kΩ
10kΩ
P4
P3
P2
P1
+IN
–V
S
+V
S
OUT
OUT
N1
N2
N3
10
9
8
2
3
4
–IN
Figure 48. Gain = ½ Difference Amplifier, Referenced to Midsupply
=
–IN
+IN
10kΩ
10kΩ
10kΩ
10kΩ
+V
S
+ –V
S
2
07363-057
1
7
10kΩ
AD8271
10kΩ
10kΩ
10kΩ
20kΩ
20kΩ
10kΩ
P4
P3
P2
P1
+IN
NC
NC
OUT
OUT
N1
N2
N3
10
9
8
2
3
4
–IN
–V
S
+V
S
Figure 49. Gain = 1 Difference Amplifier, Referenced to Midsupply
=
–IN
+IN
10kΩ
5kΩ
5kΩ
10kΩ
+V
S
+ –V
S
2
07363-058
1
7
10kΩ
AD8271
10kΩ
10kΩ
10kΩ
20kΩ
20kΩ
10kΩ
P4
P3
P2
P1
+IN
–V
S
+
V
S
OUT
OUT
N1
N2
N3
10
9
8
2
3
4
+IN
Figure 50. Gain = 2 Difference Amplifier, Referenced to Midsupply
Table 8. Pin Connections for Difference Amplifier Configurations
Configuration
Gain and Reference
Pin 1
(P1)
Pin 2
(P2)
Pin 3
(P3)
Pin 4
(P4)
Pin 8
(N1)
Pin 9
(N2)
Pin 10
(N3)
Gain of ½, Referenced to Ground +IN GND GND GND OUT
OUT
−IN
Gain of ½, Referenced to Midsupply +IN −V
S
+V
S
+V
S
OUT
OUT
−IN
Gain of 1, Referenced to Ground +IN NC GND GND OUT
NC
−IN
Gain of 1, Referenced to Midsupply +IN NC −V
S
+V
S
OUT
NC
−IN
Gain of 2, Referenced to Ground +IN +IN GND GND OUT
−IN
−IN
Gain of 2, Referenced to Midsupply +IN +IN −V
S
+V
S
OUT
−IN
−IN