Texas Instruments SN74LS138N ?C 3-to-8 Decoder for Address Decoding and Logic Expansion
The SN74LS138N is a high-speed TTL-compatible 3-to-8 line decoder/demultiplexer designed for address decoding, signal routing, and memory selection applications. Developed by IC Manufacturer, this device offers expanded enable input functionality, allowing for cascading and flexible logic structures across digital systems.
With three binary select inputs (A, B, C), the device activates one of eight outputs, depending on the logic state. The SN74LS138N??s outputs are active low, and only one will be enabled at any given time, ensuring precise control in complex logic environments.
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Electrical Specifications and Pin Configuration
| Parameter | Value | Unit |
|---|---|---|
| Logic Type | 3-to-8 Line Decoder/Demultiplexer | – |
| Inputs | 3 (A, B, C) | – |
| Outputs | 8 (Active Low) | – |
| Enable Inputs | 3 (2 Active Low, 1 Active High) | – |
| Propagation Delay | 18 | ns |
| Supply Voltage (Vcc) | 5 | V |
| Output Current | 8 (Sink) | mA |
| Package | DIP-16 | – |
Why Choose SN74LS138N Decoder?
- Expanded Control: Three enable inputs allow for hierarchical decoding and easy cascading of multiple devices.
- Low Power Design: TTL logic technology minimizes power dissipation, enabling use in energy-sensitive systems.
- Fast Switching: With an 18ns propagation delay, it ensures rapid signal transitions for high-speed systems.
- Compatible Design: DIP-16 packaging allows for standard breadboard and PCB compatibility.
Typical Applications
- Memory Address Decoding
- Logic Gate Expansion in CPUs and MCUs
- Peripheral Chip Selection in Embedded Systems
- Signal Demultiplexing for Digital Control
- Programmable Logic Boards and Trainer Kits
Frequently Asked Questions (FAQ)
What is the function of the SN74LS138N?
This decoder takes a 3-bit binary input and selects one of eight active-low outputs. It is used for address decoding, signal routing, or chip selection in digital systems.
Can it be cascaded with other decoders?
Yes. With three enable inputs (two active-low and one active-high), the SN74LS138N can be easily cascaded with other decoders to expand logic levels beyond 3-to-8 selection.
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Is the SN74LS138N suitable for TTL systems?
Absolutely. It??s built using TTL logic and is fully compatible with standard TTL voltage and current specifications, including logic thresholds and fan-out capabilities.
What kind of applications use this decoder?
It??s used widely in embedded systems, memory decoding, CPU control signal generation, and any circuit needing deterministic one-of-many selection logic.
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How is it packaged for use?
The device is available in a DIP-16 through-hole package, making it perfect for educational kits, prototypes, and final hardware designs requiring robustness and ease of placement.
