Analog Devices UG-469, Руководство пользователя

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UG-469 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 6 shows the available configurations.
The noninverting amplifier with linear gain is shown in Figure 4,
and the gain is defined in Equation 3.
AW2
WB2
R
R
G
+ =
1 (3)
where:
R
WB2
is the code loaded for the R
WB2
resistance.
R
AW2
is the code loaded for the R
AW2
resistance.
1
1006-
004
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
A2 B2
W2
R41
1.7k
Ω
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.
RDAC2
RDAC2
G
−
+ =
256
1 (4)
where:
RDAC2 is the code loaded in the RDAC2.
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
A2 B2
W2
R41
1.7k
Ω
A2
R43
1
1006-
005
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.
AW2
WB2
R
R
G
− =
(5)
where:
R
WB2
is the code loaded for the R
WB2
resistance.
R
AW2
is the code loaded for the R
AW2
resistance.
1
1006-
006
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
W2
A2 B2
R41
1.7kΩ
R43
A2
Figure 6. Linear Inverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
The inverting amplifier with pseudologarithmic gain is shown
in Figure 7, and the gain is defined in Equation 6.
2 256
2
RDAC
RDAC
G
−
− =
(6)
where:
RDAC2
is the code loaded in the RDAC2.
1
1006-
007
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
W2
A2 B2
R41
1.7kΩ
R43
A2
Figure 7. Pseudologarithmic Inverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
Output Buffers
RDAC3 and RDAC4 can be connected to an output buffer as
shown Figure 8 and Figure 9.
VOUT3
RDAC3
A3
B3
BUF_3
A3
B3
W3
W3
1
1006-
008
Figure 8. RDAC3
VOUT4
RDAC4
A4
B4
BUF_4
A4
B4
W4
W4
1
1006-
009
Figure 9. RDAC4