74148 IC 8-to-3 Line Priority Encoder
The IC 74148 is an 8-to-3 line priority encoder that takes eight active-low input lines and encodes the highest-priority active input into a 3-bit binary output. The inputs range from I0 (lowest priority) to I7 (highest priority), and only one binary code appears at the output for the highest-numbered active-low input.
This encoder includes Enable Input (EI), Group Select (GS), and Enable Output (EO) lines for cascading multiple encoders in large systems. The outputs A0, A1, and A2 represent the binary value of the highest-priority input that is LOW. If no input is active (all HIGH), the output stays inactive and EO is HIGH.
The IC 74148 is commonly used in interrupt handling, data prioritization, channel selection, and control signal generation. Its compact logic and fast response suit high-speed digital applications where managing multiple request signals is essential.
Key Features
Encodes 8 active-low inputs into 3-bit binary output
Assigns fixed priority (I7 highest, I0 lowest)
Cascadable using Enable In, Group Select, and Enable Out
TTL-compatible input/output levels
Fast response time
Compact DIP-16 or SOIC-16 packaging
Ideal for interrupt or polling systems
Applications
Convert multiple request signals into a binary code
Handle prioritized interrupts in microcontroller systems
Select input channels in multiplexed systems
Encode control lines in digital communication circuits
Implement polling logic in CPU or bus management
Reduce data lines in keyboard or panel scanners
Build hierarchical logic systems with nested priorities
Assign hardware priorities in industrial controllers
Manage status reporting in fault-detection logic
Use in digital logic teaching and lab experiments
Specifications Table
| Parameter | Value |
|---|---|
| Logic Family | TTL |
| Function | 8-to-3 Line Priority Encoder |
| Input Lines | 8 (I0 to I7, active LOW) |
| Output Lines | 3 (A0, A1, A2) + EO, GS |
| Enable Input (EI) | Active LOW |
| Enable Output (EO) | Active LOW |
| Group Select (GS) | Active LOW |
| Output Type | TTL Push-Pull |
| Input HIGH Voltage | ≥ 2.0V |
| Input LOW Voltage | ≤ 0.8V |
| Output HIGH Voltage | ≥ 2.4V |
| Output LOW Voltage | ≤ 0.4V |
| Propagation Delay | ~22 ns ‘ |
| Supply Voltage (Vcc) | 4.75V to 5.25V |
| Operating Temperature | 0°C to 70°C |
| Package Type | DIP-16 / SOIC-16 |
| Number of Pins | 16 |
