Product Overview
Harris CD74HC138E 16-Pin DIP Decoder - 74HC138 CMOS Logic, Active-Low Outputs, Unused NOS
Condition
Unused NOS. Markings legible: CD74HC138E, Harris logo, lot code H 9414 (14th week of 1994 production). All 16 leads straight, clean, and free of corrosion. Sourced from an electronics distributor consolidating inventory.
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Product Overview
Harris Semiconductor CD74HC138E - a 74HC-series high-speed CMOS 3-to-8 line decoder/demultiplexer in a 16-pin PDIP through-hole package. Three binary select inputs (A0, A1, A2) drive one of eight active-low outputs. Three enable inputs (two active-low, one active-high) give full control over output activation. Operates on 2V to 6V supply. Typical propagation delay of 13ns at 5V. Direct drop-in for 74HC138 sockets in vintage and modern circuits alike.
Key Features
- Function: 3-to-8 line decoder/demultiplexer with inverting (active-low) outputs
- Supply voltage: 2V to 6V
- Propagation delay: 13ns typical at 5V
- Package: 16-pin PDIP, through-hole - plugs directly into standard DIP sockets and breadboards
- Three enable inputs for cascading and bus control
- High-speed CMOS (HC) logic family - CMOS-level inputs
- Operating temperature: -55°C to 125°C
- Lot code H 9414 - manufactured week 14 of 1994
Applications
- Retro-computing repair: pulling a failed 74HC138 from a vintage computer board, dropping this DIP straight into the socket, and verifying address decode is restored without adapter boards or rework
- Arcade board repair: swapping a dead decoder on a logic board to bring back display output or peripheral selection, using standard desoldering tools on original through-hole pads
- Breadboard prototyping: plugging the 16-pin DIP into a standard breadboard to wire up memory address decoding or chip-select logic during circuit development
- Industrial control repair: replacing a failed decoder/demultiplexer on a legacy automation board to restore data routing without circuit modifications or re-validation
- Maker and hobbyist projects: driving 8-channel LED arrays, multiplexing displays, or managing peripheral selection lines with a single 3-bit control bus
Frequently Asked Questions
Is this compatible with TTL logic outputs?
The CD74HC138E uses CMOS-level input thresholds. It will work reliably when driven by CMOS or LVTTL outputs. If your system drives it directly from classic TTL outputs, the TTL high-level voltage may fall short of the HC input high threshold at lower supply voltages - in that case, the HCT variant (CD74HCT138E) is the correct choice for direct TTL compatibility.
What outputs does this provide - active-high or active-low?
Active-low. The selected output goes low; all others remain high. If your application needs active-high outputs, external inversion is required.
Does this include a datasheet or documentation?
Not included. The CD74HC138 / 74HC138 is a widely documented standard logic device and datasheets are available from multiple sources.
What is the "E" suffix in CD74HC138E?
The "E" suffix designates the PDIP (Plastic Dual In-line Package) - the standard 16-pin through-hole package. Surface-mount versions of the same device carry different suffix letters (e.g., "M" for SOIC).
A 1994-vintage Harris decoder that has been waiting thirty years for the right repair job - leads straight, markings sharp, ready to drop into the socket and close the loop.
