4017 Decade Counter with 10 Decoded Outputs

A CD4017 CMOS integrated circuit providing a decade counter with 10 decoded outputs. Counts clock pulses and raises one of ten outputs in turn. The classic chip behind chase lights, running LED displays and simple sequencers - it needs no decoding logic because the outputs are already decoded. 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