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Texas Instruments SN74LS125ANS

Name: SN74LS125ANS
Brand: Texas Instruments
SKU: SN74LS125ANS
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LS125ANS

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 14-SOIC (0.209", 5.30mm Width)

Datasheet:: SN74LS125ANS.pdf

Description:: PROTOTYPE

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Product details

Overview

SN74LS125ANS from Texas Instruments is a quad 3-state bus buffer IC with independent channel enable control, designed for TTL-compatible digital bus interfacing in legacy industrial and computing systems. It features low-impedance active outputs (I_OL = 24 mA, I_OH = –2.6 mA), high-impedance off-state isolation, and operates at V_CC = 4.5–5.5 V across 0°C to 70°C. Its primary role is bidirectional data bus buffering with per-channel output disable via active-high G inputs.

For engineers reviewing the SN74LS125ANS datasheet, SN74LS125ANS pinout, SN74LS125ANS application, or SN74LS125ANS equivalent, this page delivers verified electrical specs, SOP-14 package details, real-world use cases in bus arbitration and level translation, and two confirmed alternative parts with documented functional and timing differences.

Technical Context

The SN74LS125ANS implements four independent non-inverting buffer gates, each with a dedicated active-high output-enable input (G). When G = HIGH, the output Y follows input A; when G = LOW, Y enters high-impedance state. Its LS-TTL circuitry uses bipolar transistor logic with Schottky clamping, delivering improved speed-power trade-offs over standard TTL while maintaining pin-level compatibility with the '125 family.

It supports heavy capacitive bus loading without external pull-ups due to enhanced high-level drive capability (V_OH ≥ 2.4 V at I_OH = –2.6 mA) and fast switching (t_PLH/t_PHL ≤ 15 ns typical at V_CC = 5 V, T_A = 25°C, R_L = 667 Ω, C_L = 45 pF). All channels operate independently-no shared enable or internal bus contention logic.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	4.5 V to 5.5 V - Ensures stable operation within standard TTL supply tolerance; not rated for 3.3 V or wide-voltage rails.
I_OL (Low-level Output)	24 mA - Sufficient to sink current from multiple TTL loads or drive LEDs directly without series resistors.
I_OH (High-level Output)	–2.6 mA - Provides robust high-level drive into capacitive buses, eliminating need for external pull-up resistors.
t_PLH/t_PHL	9–15 ns (typ) - Enables reliable operation in sub-20 MHz synchronous bus environments with predictable setup/hold margins.
Input Thresholds	V_IL ≤ 0.8 V, V_VIH ≥ 2.0 V - Matches standard TTL logic levels; compatible with 74LS, 74S, and original 74-series outputs.
Quiescent Current	I_CC = 11–20 mA (max) - Lower than standard 74125 (32–54 mA), reducing thermal load in dense PCB layouts.

Pinout & Package

SOP-14 (NS package), 14-pin small-outline plastic package, 1.27 mm pitch, 8.75 mm × 4.0 mm body, 1.75 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1 (260°C peak reflow).

Pin/Terminal	Circuit Role	Design Meaning
1G, 2G, 3G, 4G	Active-high output enable (per channel)	Drives corresponding Y output to high-Z when LOW; enables buffer action when HIGH.
1A–4A	Data inputs	Non-inverting logic inputs; accept standard TTL voltage thresholds (V_IL ≤ 0.8 V, V_VIH ≥ 2.0 V).
1Y–4Y	3-state buffered outputs	Drive bus lines actively when enabled; present >100 kΩ impedance when disabled-no loading or contention.
V_CC (Pin 14)	Positive supply	Must be decoupled locally (0.1 µF ceramic) to suppress switching noise on shared bus power rails.
GND (Pin 7)	Ground reference	Common return for all inputs, outputs, and internal bias networks; requires low-impedance PCB connection.

Key Features

Feature	Design Value
Independent per-channel 3-state control	Enables selective bus segment isolation-e.g., disable only one memory bank while others remain active.
Enhanced high-level output drive	Delivers 2.4 V minimum at –2.6 mA, allowing direct driving of heavily loaded TTL buses without pull-up resistors.
Low quiescent power vs. standard TTL	11–20 mA I_CC (vs. 32–54 mA for SN74125) reduces board-level heat generation and improves system efficiency.
TTL-compatible input thresholds	V_IL ≤ 0.8 V / V_VIH ≥ 2.0 V ensures interoperability with legacy 74xx, 74LSxx, and 74Sxx logic families.
Fast enable/disable transitions	t_PZH/t_PZL ≤ 25 ns (max) minimizes bus turnaround time in bidirectional data transfer protocols.

Applications

Industrial Control Backplane	Legacy Computer Memory Expansion
Use Scenario: Isolating CPU address/data bus segments from multiple peripheral modules on a DIN-rail mounted PLC backplane. IC Role / Device Role / Timing Role: SN74LS125ANS acts as a direction-controlled bus repeater, enabling hot-swap-safe module insertion by disabling unused channel outputs during configuration. Use Value: Prevents bus contention during module insertion/removal and eliminates need for discrete pull-up networks on 16-bit parallel address lines.	Use Scenario: Interfacing an ISA-bus expansion card with a vintage 80286-based motherboard requiring strict TTL voltage compliance. IC Role / Device Role / Timing Role: SN74LS125ANS buffers and isolates memory-mapped I/O signals between the ISA slot and local FPGA logic, with per-line enable matching address decode windows. Use Value: Maintains signal integrity across 10+ inch trace lengths while meeting t_PLH/t_PHL < 15 ns timing budget for 8 MHz ISA cycles.
Test Equipment Signal Routing	Automated Test Fixture Bus Arbitration
Use Scenario: Multiplexing stimulus signals from multiple DUT interfaces onto a shared analog-to-digital acquisition path in benchtop ATE. IC Role / Device Role / Timing Role: SN74LS125ANS provides channel-selectable signal gating-only one buffer enabled at a time-to prevent cross-talk between DUT channels. Use Value: Achieves >60 dB off-isolation between channels without relays or analog switches, reducing fixture cost and calibration complexity.	Use Scenario: Managing shared JTAG or boundary-scan test access across multiple ASICs on a production test board. IC Role / Device Role / Timing Role: SN74LS125ANS isolates TDI/TDO lines per device under test, with enable signals synchronized to test controller's scan chain sequencing. Use Value: Eliminates need for software-managed tri-state delays; hardware-level bus arbitration ensures deterministic TCK edge alignment across devices.

Industrial Control Backplane

Legacy Computer Memory Expansion

Use Scenario: Isolating CPU address/data bus segments from multiple peripheral modules on a DIN-rail mounted PLC backplane.

IC Role / Device Role / Timing Role: SN74LS125ANS acts as a direction-controlled bus repeater, enabling hot-swap-safe module insertion by disabling unused channel outputs during configuration.

Use Value: Prevents bus contention during module insertion/removal and eliminates need for discrete pull-up networks on 16-bit parallel address lines.

Use Scenario: Interfacing an ISA-bus expansion card with a vintage 80286-based motherboard requiring strict TTL voltage compliance.

IC Role / Device Role / Timing Role: SN74LS125ANS buffers and isolates memory-mapped I/O signals between the ISA slot and local FPGA logic, with per-line enable matching address decode windows.

Use Value: Maintains signal integrity across 10+ inch trace lengths while meeting t_PLH/t_PHL < 15 ns timing budget for 8 MHz ISA cycles.

Test Equipment Signal Routing

Automated Test Fixture Bus Arbitration

Use Scenario: Multiplexing stimulus signals from multiple DUT interfaces onto a shared analog-to-digital acquisition path in benchtop ATE.

IC Role / Device Role / Timing Role: SN74LS125ANS provides channel-selectable signal gating-only one buffer enabled at a time-to prevent cross-talk between DUT channels.

Use Value: Achieves >60 dB off-isolation between channels without relays or analog switches, reducing fixture cost and calibration complexity.

Use Scenario: Managing shared JTAG or boundary-scan test access across multiple ASICs on a production test board.

IC Role / Device Role / Timing Role: SN74LS125ANS isolates TDI/TDO lines per device under test, with enable signals synchronized to test controller's scan chain sequencing.

Use Value: Eliminates need for software-managed tri-state delays; hardware-level bus arbitration ensures deterministic TCK edge alignment across devices.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS125AN	Same logic function and DC specs, but in 14-pin PDIP (N) package with through-hole mounting and no RoHS exemption.	Preferred for prototyping, repair of legacy equipment, or wave-soldered industrial assemblies where SOP reflow is impractical.	Select SN74LS125AN if board assembly uses through-hole processes or requires legacy footprint compatibility with existing schematics.
SN74LS244N	Octal (8-channel) non-inverting buffer with dual 4-bit groups, shared OE# controls per group, higher I_OL (24 mA per output), identical V_CC/timing specs.	Better suited for full 8-bit data bus buffering; lacks per-channel enable granularity of SN74LS125ANS.	Choose SN74LS244N when consolidating multiple SN74LS125ANS functions onto one IC to reduce component count on new designs with 8-bit-wide paths.

Compared with SN74LS125AN, the SN74LS125ANS offers surface-mount reliability and RoHS compliance for modern manufacturing, while SN74LS244N trades per-channel control for higher density-making it optimal for full-byte bus buffering where group-level enable suffices.

Availability

SN74LS125ANS is available at Aetrix Electronics and suitable for industrial control backplanes, legacy computer memory expansion, automated test fixture bus arbitration, and benchtop signal routing requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS125ANS 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74LS125ANS belongs to TI's legacy 74LS logic family, engineered for backward compatibility with 74-series TTL systems while delivering lower power and improved noise immunity for retro-computing, military avionics spares, and industrial retrofit applications.

FAQ

What is the maximum operating temperature range for the SN74LS125ANS?

The SN74LS125ANS is rated for operation from 0°C to +70°C ambient temperature. This commercial-grade specification aligns with its SOP-14 (NS) packaging and distinguishes it from military-grade variants like SN54LS125AJ (–55°C to +125°C). Operation outside this range may cause parameter drift or latch-up.

Does the SN74LS125ANS support 3.3 V logic interfacing?

No-the SN74LS125ANS is strictly a 5 V TTL device with V_CC = 4.5–5.5 V and input thresholds defined for 5 V operation (V_IL ≤ 0.8 V, V_VIH ≥ 2.0 V). Direct connection to 3.3 V logic risks undriven inputs or marginal noise margins; level-shifting circuitry is required for mixed-voltage systems.

Can the SN74LS125ANS replace the SN74125 in an existing design?

Yes-SN74LS125ANS is a drop-in functional replacement for SN74125 in most cases: same pinout (SOP-14), identical logic behavior, and improved specs (lower I_CC, faster t_PLH/t_PHL). However, verify that the LS version's reduced input current (I_IL = –0.4 mA vs. –1.6 mA for '125) does not affect upstream driver loading in high-fanout configurations.

What is the meaning of "NS" in SN74LS125ANS?

"NS" denotes the SOP (Small Outline Package) variant per TI's package coding-specifically the 14-pin SOP with 1.27 mm lead pitch and gull-wing leads. It is distinct from "N" (PDIP), "D" (SOIC), and "DB" (SSOP) packages. The "R" suffix in SN74LS125ANSR indicates tape-and-reel packaging; the base part number SN74LS125ANS refers to the device itself.

Is the SN74LS125ANS pin-compatible with SN74LS126A?

No-SN74LS125ANS and SN74LS126A share the same pinout and package, but differ in enable polarity: SN74LS125ANS disables outputs when G = HIGH, whereas SN74LS126A disables when G = LOW. Swapping them without inverting control signals will invert bus enable logic and cause functional failure.

SN74LS125ANS Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LS

Package/Case:: 14-SOIC (0.209", 5.30mm Width)

Packaging:: Tube

Product Status:: Obsolete

Logic Type:: Buffer, Non-Inverting

Number of Elements:: 4

Number of Bits per Element:: 1

Input Type:: -

Output Type:: 3-State

Current - Output High, Low:: 2.6mA, 24mA

Voltage - Supply:: 4.75V ~ 5.25V

Operating Temperature:: 0°C ~ 70°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 14-SO

SN74LS125ANS FAQ

1.How can I place an order for SN74LS125ANS through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS125ANS on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SN74LS125ANS reliable?

The price and inventory of SN74LS125ANS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS125ANS is usually 5 days.

3.What payment methods are accepted for SN74LS125ANS?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS125ANS transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS125ANS?

SN74LS125ANS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS125ANS order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SN74LS125ANS?

For technical support, including SN74LS125ANS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS125ANS requirements.

6.How does Aetrix verify that SN74LS125ANS is sourced from the original manufacturer or authorized distributors?

All SN74LS125ANS products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74LS125ANS meets industry standards.

7.What is the process for return or replacement of SN74LS125ANS?

All SN74LS125ANS units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS125ANS, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SN74LS125ANS part is unused and in its original packaging.

Return procedure for SN74LS125ANS:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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