CD74HCT138E

Overview

The CD74HCT138E is a high-speed CMOS decoder/demultiplexer from the Texas Instruments 74HCT series. It features one 3-to-8 line decoder with three binary select inputs and three enable inputs (two active-low, one active-high). The device operates on a single power supply ranging from 4.5 V to 5.5 V. Outputs are active-low and can drive ten low-power Schottky TTL loads. It is housed in a 20-pin DIP package and supports an operating temperature range of -55°C to +125°C.

Feature Summary

• Provides eight mutually exclusive outputs selected by three binary address inputs
• Includes three independent enable inputs for cascading or system control
• Outputs actively driven low to interface directly with low-power Schottky TTL logic

Applications

• Memory address decoding in computer systems
• Data routing and distribution networks
• Demultiplexing digital signals to peripheral devices

Procurement Notes

Verify the specific suffix 'E' corresponds to the PDIP-20 through-hole package configuration. Confirm RoHS compliance status and moisture sensitivity level requirements against current datasheet revisions before finalizing procurement orders.

Selection Notes

Select this component when TTL-compatible input thresholds are required alongside CMOS output drive capabilities. Ensure the application environment accommodates the extended industrial temperature range and that the 20-pin DIP footprint aligns with the target PCB layout constraints.

Part Context

This part belongs to the standard 74HCT logic family, designed to bridge HC CMOS performance with TTL electrical characteristics. It serves as a foundational building block for address decoding and signal distribution within mixed-logic digital circuits requiring robust noise immunity.

Replacement Considerations

Compatible substitutes include SN74HCT138PWR and CD74HC138M96. Verify pinout compatibility and ensure voltage threshold differences between HCT and HC families do not impact circuit operation.