Each OPAMP can be configured as a buffer or a PGA for the other modules (such as ADC or AC). OPAMPs can also be cascaded to increase the programmable gain.
The output to the OPAMP must be enabled by writing a '1' to the Analog Output bit in the Operational Amplifier x Control register (OPAMPCTRLx.ANAOUT). The ADC input mux must be configured to select OPAMP as input. Refer to ADC – Analog-to-Digital Converter for details on configuring the ADC.