The ADG508F, ADG509F, and ADG528F1 are CMOS analog multiplexers, with the ADG508F and ADG528F comprising eight single channels and the ADG509F comprising four differential channels. These multiplexers provide fault protec-tion. Using a series n-channel, p-channel, n-channel MOSFET structure, both device and signal source protection is provided in the event of an overvoltage or power loss. The multiplexer can withstand continuous overvoltage inputs from ?40 V to +55 V. During fault conditions, the multiplexer input (or out-put) appears as an open circuit and only a few nanoamperes of leakage current will flow. This protects not only the multiplexer and the circuitry driven by the multiplexer, but also protects the sensors or signal sources that drive the multiplexer.