Texas Instruments SN74F126N

Overview

SN74F126N from Texas Instruments is a quadruple bus buffer gate with 3-state outputs, designed for bidirectional data bus isolation and memory address register buffering in TTL-compatible digital systems. It operates from 4.5 V to 5.5 V, delivers 6.5 ns max propagation delay at 5 V, and supports ±64 mA output drive capability per channel.

For engineers reviewing the SN74F126N datasheet, SN74F126N pinout, SN74F126N application, or SN74F126N equivalent, this device is selected for legacy TTL bus interface design, memory subsystem signal conditioning, and 3-state-controlled data path management where low skew and guaranteed high-impedance disable are required.

Technical Context

The SN74F126N implements four independent noninverting buffers, each with dedicated active-high output-enable (OE) control. Each channel transitions to high-impedance state when OE is low, enabling shared-bus arbitration without contention.

It uses bipolar F-type TTL logic architecture, ensuring compatibility with 74F-series timing and voltage thresholds. Input clamp current of –18 mA and output short-circuit current rating of –225 mA support robust transient handling during bus contention or power sequencing.

Key Specifications

Pinout & Package

SN74F126N is housed in a 14-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and through-hole mounting. Pin 1 is marked by a notch or dot; the package complies with JEDEC MS-001 and TI's D0014A outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus buffer applications.

Compared with SN74F126N, SN74LS126N trades speed and drive for lower static power, while SN74ACT126N offers voltage flexibility and CMOS robustness but lacks native TTL input threshold matching - both require schematic and timing validation before substitution.

Availability

SN74F126N is available at Aetrix Electronics and suitable for memory subsystem design, industrial backplane interfaces, and legacy test equipment requiring stable component supply with full traceability and long-term obsolescence management.

Supply support for SN74F126N includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions, with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74F126N belongs to TI's 74F TTL logic family, engineered for high-speed, noise-tolerant digital interfacing in mission-critical industrial and instrumentation systems where reliability and timing predictability are essential.

FAQ

What is the recommended pull-down resistor value for OE pins on SN74F126N?

The minimum pulldown resistor value for OE pins on SN74F126N is determined by the driver's current-sourcing capability. TI specifies that OE must be tied to GND through a pulldown resistor to guarantee high-impedance state at power-up; typical values range from 1 kΩ to 10 kΩ depending on board capacitance and rise-time requirements. The SN74F126N datasheet does not define an exact minimum resistance, but design practice uses 4.7 kΩ for robust noise immunity and fast discharge.

Does SN74F126N support mixed-voltage operation between 3.3 V and 5 V logic domains?

No, SN74F126N does not support mixed-voltage operation. It is a 5-V-only TTL device with VCC range strictly 4.5 V to 5.5 V and input thresholds fixed at VIH = 2.0 V and VIL = 0.8 V. Applying 3.3 V signals directly to its inputs may result in marginal or incorrect logic recognition. For 3.3 V–5 V interfacing, SN74F126N requires external level-shifting circuitry or should be replaced with a 5 V tolerant CMOS buffer like SN74ACT126N.

Can SN74F126N outputs safely drive a 50 Ω transmission line?

SN74F126N outputs are not designed for direct 50 Ω transmission line driving. Its output structure is optimized for TTL fanout into capacitive loads (CL = 50 pF specified), not resistive termination. Driving 50 Ω loads risks exceeding IOL = 64 mA or IOH = –15 mA limits, causing excessive voltage drop or thermal stress. For controlled-impedance routing, use SN74F126N as a logic-stage buffer followed by a dedicated line driver or series-terminate with appropriate resistor.

Is SN74F126N RoHS compliant and lead-free?

Yes, SN74F126N is RoHS compliant and features NiPdAu (NIPDAU) lead finish. Per TI's packaging addendum, the active SN74F126N variant carries "Yes" for RoHS and uses lead-free terminations. The PDIP package does not require moisture sensitivity level (MSL) rating due to its through-hole construction, and it is rated for 0°C to 70°C operation with full traceability documentation available through Aetrix Electronics.

How many SN74F126N devices are included in one tube packaging unit?

Each tube of SN74F126N contains 25 units. This standard packaging quantity is defined in TI's ordering information and confirmed in the Package Materials Information document. Tubes are used for through-hole PDIP components to support manual or wave-solder assembly processes and provide mechanical protection during handling and storage.