Analog Devices EVAL-AD5141DBZ, User Manual

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UG-473 Evaluation Board User Guide
Rev. 0 | Page 6 of 20
Signal Amplifier
The RDAC can be operated as an inverting or noninverting
signal amplifier supporting linear or pseudologarithmic gains.
Table 10 and Table 11 show the available configurations.
The noninverting amplifier with linear gain is shown in Figure 4,
and the gain is defined in Equation 3.
AW
WB
R
R
G
+ =
1 (3)
where:
R
WB
is the code loaded for the R
WB
resistance.
R
AW
is the code loaded for the R
AW
resistance.
1
1010-
004
VOUT2
V
IN
RDAC
R42
C1
10nF
W2
B2
A B
W
R41
1.7kΩ
A2
R43
Figure 4. Linear Noninverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
The noninverting amplifier with pseudologarithmic gain is
shown in Figure 5, and the gain is defined in Equation 4.
RDAC
RDAC
G
−
+ =
256
1 (4)
where:
RDAC is the code loaded in the RDAC.
1
1010-
005
VOUT2
V
IN
RDAC
R42
C1
10nF
W2
B2
A B
W
R41
1.7kΩ
A2
R43
Figure 5. Pseudologarithmic Noninverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
The inverting amplifier with linear gain is shown in Figure 6,
and the gain is defined in Equation 5.
Note that the input signal, V
IN
, must be negative.
AW
WB
R
R
G
− =
(5)
where:
R
WB
is the code loaded for the R
WB
resistance.
R
AW
is the code loaded for the R
AW
resistance.
1
1010-
006
VOUT2
V
IN
RDAC
R42
C1
10nF
W2
B2
W
A
B
R41
1.7kΩ
R43
A2
Figure 6. Linear Inverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
Table 10. Amplifier Selection Daughter Board Link Options
Link Options Description
A6 A Connects Terminal A to A2
A7 A Connects Terminal W to W2
A8 A Connects Terminal B to B2
A1 OUT Open short circuit for the AD8618
The inverting amplifier with pseudologarithmic gain is shown
in Figure 7, and the gain is defined in Equation 6.
RDAC
RDAC
G
−
− =
256
(6)
where:
RDAC is the code loaded in the RDAC.
1
1010-
007
VOUT2
V
IN
RDAC
R42
C1
10nF
W2
B2
W
A B
R41
1.7kΩ
R43
A2
Figure 7. Pseudologarithmic Inverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.