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R1
R2
VIN
-
+
VOUT1=VIN(1+ R2/R1)
VOUT2=VIN(1+ R2/R1)
VOUT3=VIN(1+ R2/R1)
R1
R2
-
+
R1
R2
-
+
Figure 24.8. Cascaded Non-inverting PGA Overview
Table 24.9 Cascaded Non-inverting PGA Configuration on page 807
shows cascaded non-inverting PGA with OPA0,OPA1 and OPA2.
When cascaded, the positive input on OPA0 is configured by the OPA0 POSSEL bit-field in VDACn_OPA0_MUX. The output from
OPA0 is connected to OPA1 to create the second stage by setting the POSSEL field to OPANEXT in VDACn_OPA1_MUX. The last
stage is created by setting the POSSEL bit-field to OPANEXT in VDACn_OPA2_MUX.
Table 24.9. Cascaded Non-inverting PGA Configuration
OPA
OPA Bitfields
OPA Configuration
OPA0
POSSEL
POSPAD0,APORT[1-4]X
OPA0
NEGSEL
OPATAP
OPA0
RESINMUX
VSS, NEGPAD0
OPA1
POSSEL
OPANEXT
OPA1
NEGSEL
OPATAP
OPA1
RESINMUX
VSS, NEGPAD1
OPA2
POSSEL
OPANEXT
OPA2
NEGSEL
OPATAP
OPA2
RESINMUX
VSS, NEGPAD2
24.3.4.7 Two Opamp Differential Amplifier
This mode allows OPA0 and OPA1 or OPA1 and OPA2 to be internally connected to form a two opamp differential amplifier as shown in
Figure 24.9 Two Op-amp Differential Amplifier Overview on page 808
. When using OPA0 and OPA1, the positive input of OPA0 can
be connected to any input by setting the POSSEL bit-field in VDACn_OPA0_MUX. The OPA0 feedback path must be configured for
unity gain by setting the NEGSEL bit-field to UG in VDACn_OPA0_MUX. In addition, the OPA0 RESINMUX bit-field must be set to DIS-
ABLED. The OPA0 NEXTOUT output must be connected to OPA1 by setting the RESINMUX bit-field to OPANEXT in
VDAC_n_OPA1_MUX. The positive input onof OPA1 is selected by the POSSELbit-field in VDACn_OPA1_MUX. The OPA1 output is
configured by DACn_OPA1_OUT.
When using OPA1 and OPA2, the positive input of OPA1 can be connected to any input by setting the POSSEL bit-field in
VDACn_OPA1_MUX. The OPA1 feedback path must be configured for unity gain by setting the NEGSEL bit-field to UG in
VDACn_OPA1_MUX. In addition, the OPA1 RESINMUX bit-field must be set to DISABLED. The OPA1 NEXTOUT output must be con-
nected to OPA2 by setting the RESINMUX bit-field to OPANEXT in VDACn_OPA2_MUX. The positive input of OPA2 is selected by the
POSSEL bit-field in VDACn_OPA2_MUX. The OPA2 output is configured by DACn_OPA2_OUT.
Reference Manual
OPAMP - Operational Amplifier
silabs.com
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