The MAX378 8-channel single-ended (1-of-8) multiplexer and the MAX379 4-channel differential (2-of-8) multiplexer use a series N-channel/P-channel/N-channel structure to provide significant fault protection. If the power supplies to the MAX378/MAX379 are inadvertently turned off while input voltages are still applied, all channels in the muxes are turned off, and only a few nanoamperes of leakage current will flow into the inputs. This protects not only the MAX378/MAX379 and the circuitry they drive, but also the sensors or signal sources that drive the muxes.