The HI-509 4-channel monolithic CMOS multiplexer includes an array of eight analog switches, a digital decoder circuit for channel selection, voltage reference for logic thresholds, and an enable input for device selection when several multiplexers are present. The Dielectric Isolation (DI) process used in fabrication of these devices eliminates the problem of latch-up. DI also offers much lower substrate leakage and parasitic capacitance than conventional junction isolated CMOS.