Analog Devices EVAL-AD5254SDZ User Manual page 5

Evaluation Board User Guide
In addition, R36 can be used to achieve a pseudologarithmic
attenuation. To do so, adjust the R36 resistor until a desirable
transfer function is found.
Signal Amplifier
RDAC1 can be operated as an inverting or noninverting signal
amplifier supporting linear or pseudologarithmic gains. Table 6
shows the available configurations.
Table 6. Amplifier Selection Link Options
Amplifier Gain
Noninverting Linear
Pseudologarithmic
Inverting Linear
Pseudologarithmic
The noninverting amplifier with linear gain is shown in Figure 4,
and the gain is defined in Equation 3.
R
= 1 + WB1
G
R38
where R is the resistor between the W1 and B1 terminals.
WB1
R41
1.7kΩ
V
IN
R38
2.7kΩ
W2
W1
RDAC1
Figure 4. Linear Noninverting Amplifier
The noninverting amplifier with pseudologarithmic gain is
shown in Figure 5, and the gain is defined in Equation 4.
R
= 1 + WB1
G
R
AW1
where:
R is the resistor between the W1 and B1 terminals.
WB1
R is the resistor between the A1 and W1 terminals.
AW1
R41
1.7kΩ
V
IN
W2
A2 W1
R43
A1
RDAC1
Figure 5. Pseudologarithmic Noninverting Amplifier
Link Label
A27 LINEAR
A29 NON-INVERTING
A30 NON- INVERTING
A27 PSEUDOLOG
A29 NON- INVERTING
A30 NON- INVERTING
A27 LINEAR
A29 INVERTING
A30 INVERTING
A27 PSEUDOLOG
A29 INVERTING
A30 INVERTING
V
OUT
C1
OAVOUT
10nF
B2
R42
B1
V
OUT
C1
OAVOUT
10nF
B2
R42
B1
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.
R
= − WB1
G
R38
where R is the resistor between the W1 and B1 terminals.
WB1
V
IN
The inverting amplifier with pseudologarithmic gain is shown
in Figure 7, and the gain is defined in Equation 6.
R
G − = WB1
R
AW1
where:
R is the resistor between the W1 and B1 terminals.
WB1
R is the resistor between the A1 and W1 terminals.
AW1
(3)
V
IN
Figure 7. Pseudologarithmic Inverting Amplifier
R43 and R42 can be used to set the maximum and minimum
gain limits.
Output Buffers
RDAC2 and RDAC3 can be connected to an output buffer as
shown Figure 8 and Figure 9.
RDAC2
(4)
RDAC3
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R41
1.7kΩ
R38
V
2.7kΩ
C1
OAVOUT
W2
10nF
B2
W1
R42
B1
RDAC1
Figure 6. Linear Inverting Amplifier
R41
1.7kΩ
C1
W2
10nF
W1
A2 B2
R43 R42
A1 B1
RDAC1
A3
W3
A2
W2 BUF_3
B2
B3
Figure 8. RDAC2
A4
W4
A3
W3
BUF_4
B3
B4
Figure 9. RDAC3
UG-236
(5)
OUT
(6)
V
OUT
OAVOUT
VOUT3
VOUT4