74HCT4017

The 74HCT4017 is a 10-stage decoded-output counter in the 74HCT logic family. It functions as a decade counter, advancing through ten outputs labeled Q0 through Q9 in sequence as clock pulses arrive. Only one of the outputs is high at a time, and after Q9 it returns to Q0 on the next clock, making it useful for stepping through a fixed sequence or driving a simple LED chaser.

Key features include a clock input for advancing the count, a reset input that asynchronously returns the counter to the initial state (with Q0 high), a clock-inhibit (CI) input to pause counting, and a carry-out (CO) output that facilitates cascading multiple counters. The device is designed to be driven with TTL-compatible signals and is part of the 74HCT family, which typically operates from a supply range around 4.5 to 5.5 volts.

Common applications include sequencing and light-display circuits, such as LED chasers, timing and pattern generation, and simple state machines where a repeatable 10-step sequence is required. Its 10 decoded outputs provide convenient, one-hot representations of each step without additional decoding logic.

The 74HCT4017 is available in standard IC packages (such as DIP and surface-mount variants) and is widely used in hobbyist and professional electronics alike. As a CMOS device with high input impedance and low static power, it pairs well with other logic gates and counters to build more complex sequential circuits.