Another App note from Texas Instruments on op-amp input safety from breakdown voltages during source switch-over. Link here (PDF)
Multiplexing is a frequently used technique to perform data acquisition in multichannel systems with minimal signal-chain requirements. In this context, the role of the multiplexer (MUX) in an acquisition system is to switch between channels, and send each signal as quickly as possible to a single data converter, thus maximizing system throughput and minimizing delay. To provide accurate processing, a precision amplifier is placed downstream from the multiplexer to precisely drive the analog-to-digital converter (ADC).