4051 8-Channel Analog Multiplexer/Demultiplexer

A CD4051 CMOS integrated circuit providing a 8-channel analogue multiplexer and demultiplexer. Connects one common line to any of eight channels under 3-bit digital control, and works with analogue signals in both directions. The standard way to expand an Arduino's analogue inputs from six to many. Being 4000-series CMOS it runs on anything from 3 to 18 volts, which makes it far more flexible than 5V-only TTL logic and lets it work directly in battery and higher voltage circuits. It also draws almost no current when idle. The trade-off is speed: CMOS of this family is slower than 74HC logic, so it suits control, timing and teaching applications rather than fast data paths. Unused inputs must be tied to a supply rail, never left floating. Wide 3-18V supply range, unlike 5V-only TTL; Extremely low quiescent current suits battery circuits; High noise immunity from the wide logic swing; Standard 16-pin DIP fits breadboards and sockets