Datasheet

UG-470 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
AW 2
is the code loaded for the R
AW2
resistance.
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
A2 B2
W2
R41
1.7kΩ
A2
R43
11007-004
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
1.7kΩ
A2
R43
11007-005
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
AW 2
is the code loaded for the R
AW2
resistance.
VOUT2
V
IN
RDAC2
R42
C1
10nF
W2
B2
W2
A2
B2
R41
1.7kΩ
R43
A2
11007-006
Figure 6. Linear Inverting Amplifier
Table 6. Amplifier Selection Link Options
Amplifier Gain Link Label Linear Setting Gain Mode Enabled
Noninverting Linear A7 LIN Yes
A6 N-INV Yes
A8 N-INV Yes
Pseudologarithmic A7 LOG No
A6 N-INV No
A8 N-INV No
Inverting Linear A7 LIN Yes
A6 INV Yes
A8 INV Yes
Pseudologarithmic A7 LOG No
A6 INV No
A8 INV No