Datasheet

Evaluation Board User Guide UG-236
Rev. 0 | Page 5 of 16
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 Link Label
Noninverting Linear A27 LINEAR
A29 NON-INVERTING
A30 NON- INVERTING
Pseudologarithmic A27 PSEUDOLOG
A29 NON- INVERTING
A30 NON- INVERTING
Inverting Linear A27 LINEAR
A29 INVERTING
A30 INVERTING
Pseudologarithmic A27 PSEUDOLOG
A29 INVERTING
A30 INVERTING
The noninverting amplifier with linear gain is shown in Figure 4,
and the gain is defined in Equation 3.
R38
R
G
WB1
+= 1
(3)
where R
WB1
is the resistor between the W1 and B1 terminals.
V
IN
RDAC1
B1
R42
W1
B2
W2
V
OUT
OAVOUT
C1
10nF
R41
1.7kΩ
R38
2.7kΩ
09579-004
Figure 4. Linear Noninverting Amplifier
The noninverting amplifier with pseudologarithmic gain is
shown in Figure 5, and the gain is defined in Equation 4.
AW1
WB1
R
R
G +=1
(4)
where:
R
WB1
is the resistor between the W1 and B1 terminals.
R
AW 1
is the resistor between the A1 and W1 terminals.
V
IN
RDAC1
B1A1
R42
W1
B2
W2
V
OUT
OAVOUT
A2
C1
10nF
R41
1.7kΩ
R43
09579-005
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.
R38
R
G
WB1
−=
(5)
where R
WB1
is the resistor between the W1 and B1 terminals.
V
IN
RDAC1
B1
R42
W1
B2
W2
V
OUT
OAVOUT
C1
10nF
R41
1.7kΩ
R38
2.7kΩ
09579-006
Figure 6. Linear Inverting Amplifier
The inverting amplifier with pseudologarithmic gain is shown
in Figure 7, and the gain is defined in Equation 6.
AW1
WB1
R
R
G −=
(6)
where:
R
WB1
is the resistor between the W1 and B1 terminals.
R
AW 1
is the resistor between the A1 and W1 terminals.
V
IN
RDAC1
B1A1
R42
W1
B2
W2
V
OUT
OAVOUT
A2
C1
10nF
R41
1.7kΩ
R43
09579-007
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.
09579-008
VOUT3
RDAC2
A2
B2
BUF_3
A3
B3
W2
W3
Figure 8. RDAC2
09579-009
VOUT4
RDAC3
A3
B3
BUF_4
A4
B4
W3
W4
Figure 9. RDAC3