SN74LS138NS

Overview

The SN74LS138NS is a 3-to-8 line decoder and demultiplexer from the Texas Instruments SN74LS series. It features three binary address inputs (A, B, C) and eight active-low outputs (Y0–Y7). The device includes three enable inputs: two active-low (G2A, G2B) and one active-high (G1), which must be in specific states for operation. It operates on a single 5V supply with a voltage range of 4.75V to 5.25V. The component is housed in a 16-pin DIP package and supports a propagation delay of 41 ns.

Feature Summary

• Provides decoding of three binary bits into eight mutually exclusive active-low outputs
• Includes three independent enable inputs to control chip activation state
• Supports direct interface with standard TTL logic families

Applications

• Address decoding for memory systems
• Data distribution in digital circuits
• Implementation of complex combinational logic functions

Procurement Notes

Verify that the ordering suffix 'N' corresponds to the plastic DIP-16 package variant rather than tape-and-reel or surface-mount options. Confirm the manufacturer is Texas Instruments to ensure compatibility with original datasheet specifications. Check RoHS compliance status as manufacturing processes may vary by production batch. Ensure the component meets the required operating temperature range of 0°C to 70°C for your specific application environment.

Selection Notes

Select this component when a standard 3-to-8 decoder with active-low outputs is required within the LS TTL family. It is suitable for designs needing multiple enable controls for system synchronization. Consider alternative packages if surface-mount technology is preferred over through-hole DIP construction. Verify power supply stability within the 4.75V to 5.25V range to maintain signal integrity.

Part Context

This part belongs to the widely used 74LS138 family of decoders manufactured by Texas Instruments. It serves as a fundamental building block in digital electronics for converting binary codes into one-hot encoded signals. The SN74LS138NS specifically denotes the through-hole DIP version, distinguishing it from SOIC or TSSOP variants like the SN74LS138D or SN74HCS138PWR.

Replacement Considerations

Compatible substitutes include SN74LS138DR and SN74LS138N from Texas Instruments. Other manufacturers produce equivalent parts such as HD74LS138P. Ensure pinout compatibility and electrical characteristics match before substitution.