74HC148 / 74148 – 8-to-3 Priority Encoder IC

Product Description

The 74HC148 / 74148 is an 8-to-3 priority encoder IC designed to convert one of eight input signals into a 3-bit binary output. It includes priority logic, meaning that when multiple inputs are active at the same time, the input with the highest priority is encoded at the output.

The IC features active-low inputs and outputs and includes enable and cascading functions, making it suitable for expanding encoder systems and building more complex digital logic circuits.

Key Features

• 8-to-3 line priority encoder.
• Converts 8 input lines into a 3-bit binary code.
• Priority logic for handling multiple active inputs.
• Active-low data inputs and outputs.
• Enable input and enable output for cascading.
• Wide operating voltage range for the 74HC version: 2V to 6V.
• High-speed CMOS logic.
• Low power consumption.
• 16-pin DIP package available.
• Compatible in function and pin configuration with the traditional 54/74LS148 family.

Technical Specifications

Applications

• Digital logic circuits.
• Priority encoding.
• Keypad and button input encoding.
• Digital control systems.
• Data encoding.
• Code converters.
• Microcontroller input expansion.
• Computer and embedded logic circuits.
• Educational electronics projects.
• Cascaded encoder systems.

How It Works

The IC monitors its eight active-low input lines and produces a corresponding 3-bit binary output. If more than one input is active simultaneously, the encoder gives priority to the input with the highest priority and ignores the lower-priority inputs.

The Enable Input (EI) and Enable Output (EO) allow multiple 74HC148 ICs to be cascaded to create larger priority encoder systems without requiring additional external logic.

Important Note

The 74HC148 and the older 74148 / 74LS148 are functionally related but belong to different logic families. The 74HC version uses CMOS technology and supports a 2V–6V supply range, while the traditional 74LS148 is designed around 5V TTL operation. Always verify the exact IC marking and electrical specifications before replacing one with another.