1.3.2 Scaling with a Programmable Gain Amplifier (PGA)

PGA is a description for amplifiers set to specific discrete gains. PGA functionality can be implemented with an operational amplifier and an internal resistor ladder, as mentioned in Scaling with an Operational Amplifier Peripheral.

However, some devices contain a dedicated PGA for the ADC. In this case, the PGA input is capacitive and will be treated as a direct input into the ADC. Capacitive PGAs can perform better than an op amp-based solution due to the lower noise voltage introduced into the signal. Using the PGA will increase the amount of time to sample a signal, which reduces the sampling rate and thus the bandwidth of the ADC.