7406

The 7406 is a member of the 7400-series integrated circuits, a hex inverter buffer with open-collector outputs. It contains six independent inverters in a single package. Each inverter accepts a logic input and controls its own open-collector output transistor. When the input is high, the transistor conducts and the output is pulled toward ground. When the input is low, the transistor is off, and an external pull-up resistor defines the output as high.

Because the outputs are open-collector, they cannot source current. They must be paired with pull-up resistors at the outputs. This arrangement allows outputs from multiple devices to be wired together for a wired-AND function, and it permits the outputs to be pulled up to voltages higher than the 5V supply (commonly up to about 30V, depending on variant). The device is typically powered from a 5V supply (approximately 4.75–5.25V). Packages include the standard 14-pin DIP, as well as surface-mount variants in modern families.

History and variants: The 7406 originated in the early 1970s as part of the TTL 7400 family developed by manufacturers such as Texas Instruments. The traditional designation is SN7406, with variants such as 74LS06 (low-power Schottky TTL) and 74HC06 (high-speed CMOS) offering different speed, power, and voltage characteristics. Applications include buffering and level shifting, driving loads that require a current sinking path, and implementing simple wired-AND networks on shared buses. The 7406 remains a common reference point in discussions of vintage and mixed-technology digital designs.

See also: 7400 family, 7404, 7408, 74LS06, 74HC06.