Texas Instruments MSP430x4xx - Manual (Page 316)

OA
16-9 OA
Figure 16−4 shows an example of a three-opamp differential amplifier using
OA0, OA1 and OA2. The control register settings are shown in Table 16−4.
The gain for the amplifier is selected by the OAFBRx bits of OA0 and OA2. The
OAFBRx settings for both OA0 and OA2 must be equal. The gain settings are
shown in Table 16−5. The OAx interconnections are shown in Figure 16−5.
Table 16−4.Three-Opamp Differential Amplifier Control Register Settings
Register Settings (binary)
OA0CTL0 00 xx xx 0 0
OA0CTL1 xxx 001 0 x
OA1CTL0 00 xx xx 0 0
OA1CTL1 000 111 0 x
OA2CTL0 11 11 xx x x
OA2CTL1 xxx 110 0 x
Table 16−5.Three-Opamp Differential Amplifier Gain Settings
OA0/OA2 OAFBRx Gain
000 0
001 1/3
010 1
011 1 2/3
100 3
101 4 1/3
110 7
111 15
Figure 16−4. Three Opamp Differential Amplifier
OA1
+
−
OA2
+
−
1
2 ) 1 2 (
R
xR V V
Vdiff
−
=
R2 R1
V2
V1
OA0
+
−
R2 R1