CMOS Analogue Switches—Structure and Specifications

Complementary metal-oxide semiconductor (CMOS) analog switches are the solid state equivalent of mechanical switches (toggle, pushbutton, and relay). Unlike their mechanical equivalents, these switches have no moving parts and are free of contact bounce, contact deterioration, and fatigue-induced lifetime limits. They require very low power to operate, are able to switch in tens of nanoseconds or faster, and naturally support analog swings up to and including the power rails. Unlike their mechanical equivalents, CMOS analog switches have variable on resistance, temperature sensitive leakage currents, and significant current handling limits.

This paper provides an overview of analog switch structure and operation, and of the designer specifications that are used to describe overall operation.