A single CMOS switch or a single channel of a CMOS multiplexer essentially consists of an N-channel and a P-channel MOSFET transistor in parallel as outlined in the diagram. The respective drains and sources of the two transistors are tied together to become the switch terminals, while the gates of the two transistors are driven to control the on/off action of the switch. Essentially, the N-channel is on for positive gate-to-source voltages and off for negative gate-to-source voltages, while the P-channel does just the opposite.