SN74LS Low-Power Schottky TTL Logic Variants

Texas Instruments SN74LS parts are 5 V Low-Power Schottky TTL logic devices used in legacy gates, buffers, counters, latches, decoders, and bus-interface circuits.

Technology

Preserves behavior expected by many 5 V legacy logic designs.

Supply rail

Not intended for low-voltage 1.8 V or 3.3 V logic rails.

Catalog depth

Includes gates, sequential logic, decoders, and bus-interface parts.

Legacy 5 V TTL logic for maintenance and compatible redesigns

Compare SN74LS functions by logic role, package, fanout, temperature grade, and replacement constraints.

The SN74LS family is Texas Instruments' Low-Power Schottky TTL logic line, widely used in 5 V digital systems before CMOS logic became dominant. The family covers standard gates, inverters, open-collector outputs, decoders, counters, latches, flip-flops, bus buffers, and transceivers. It remains important for industrial controls, test fixtures, service parts, and long-life equipment where an existing PCB or firmware timing model depends on LS-family behavior.

SN74LS devices typically operate from a 4.75 V to 5.25 V supply range and use TTL input thresholds, which makes them electrically different from HC CMOS logic even when the truth table is the same. When replacing an LS part, check input current, output sink/source capability, propagation delay, fanout, open-collector requirements, package pinout, and commercial versus industrial temperature grade. A CMOS substitute can work in some designs, but only after signal levels and loading are reviewed.

Key Features

Established TTL logic behavior for legacy 5 V systems
Broad coverage of standard 74-series functions
Useful for repair, second-source review, and long-life industrial products
Open-collector and bus-interface variants available in the family
Requires careful loading checks when replacing with CMOS families

Target Applications

Legacy industrial control boards
Test and measurement fixtures
Service and repair inventory
5 V TTL bus buffering
Counter, latch, and decoder logic

Ordering Variants

Compare 292 SN74LS part numbers by package, electrical parameters, lifecycle, and availability. Use RFQ for stock and lead-time confirmation.

Part Number	Description	Package Type	Manufacturer	Lifecycle	RoHS	Availability	Action
SN74LS126AN	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Number of Channels: 4 \| Number of Outputs: 4 \| Number of Bits: 4 \| Logic Function: Buffer, Inverting	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS365AN	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 24mA \| Max Output Current: 24mA \| Number of Channels: 6 \| Number of Outputs: 6	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS367AN	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Number of Channels: 6 \| Number of Outputs: 6 \| Number of Bits: 6 \| Logic Function: Buffer, Inverting	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS640-1N	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Number of Channels: 8 \| Number of Outputs: 8 \| Number of Bits: 8 \| Logic Function: Transceiver, Inverting	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS160AD	Number of Bits: 4 \| Max Operating Temp: 70 \| Min Operating Temp: 0 \| Number of Pins: 16 \| Terminal Position: DUAL \| Jedec Package Code: R-PDSO-G16	-	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS162AD	Number of Bits: 4 \| Max Operating Temp: 70 \| Min Operating Temp: 0 \| Number of Pins: 16 \| Terminal Position: DUAL \| Jedec Package Code: R-PDSO-G16	-	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS192D	Number of Bits: 4 \| Max Operating Temp: 70 \| Min Operating Temp: 0 \| Number of Pins: 16 \| Terminal Position: DUAL \| Jedec Package Code: R-PDSO-G16	-	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS592N	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Number of Bits: 8 \| Frequency: 35MHz \| Logic Function: Counter \| Max Operating Temp: 70°C	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS669N	Package: PDIP \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Frequency: 32MHz \| Max Frequency: 32MHz \| Logic Function: Counter \| Max Operating Temp: 70°C \| Min Operating Temp: 0°C	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS697N	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Number of Bits: 4 \| Frequency: 20MHz \| Logic Function: Counter \| Max Operating Temp: 70°C	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS90N	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 400uA \| Number of Bits: 4 \| Frequency: 42MHz \| Logic Function: Counter	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS112ADR	Package: SOIC \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Number of Bits: 2 \| Frequency: 45MHz \| Logic Function: Flip-Flop, JK-Type	SOIC	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS173AN	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 24mA \| Number of Bits: 4 \| Frequency: 50MHz \| Max Frequency: 50MHz	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS174N	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Number of Bits: 6 \| Frequency: 40MHz \| Max Frequency: 40MHz	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS175D	Package: SOIC \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Number of Bits: 4 \| Frequency: 40MHz \| Logic Function: D-Type, Flip-Flop	SOIC	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS377DW	Package: SOIC \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Number of Bits: 8 \| Frequency: 40MHz \| Max Frequency: 40MHz	SOIC	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS08N	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Max Output Current: 8mA \| Number of Outputs: 1 \| Number of Bits: 4	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS10D	Package: SOIC \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Max Output Current: 8mA \| Number of Outputs: 1 \| Number of Bits: 3	SOIC	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS132D	Package: SOIC \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Number of Outputs: 1 \| Number of Bits: 4 \| Logic Function: NAND GATE	SOIC	Texas Instruments	Active	Compliant	In Stock	RFQ
SN74LS14N	Package: PDIP \| Operating Supply Voltage: 5V \| Max Supply Voltage: 5.25V \| Min Supply Voltage: 4.75V \| Output Current: 8mA \| Max Output Current: 8mA \| Number of Bits: 6 \| Logic Function: Buffer, Inverter, Schmitt Trigger	PDIP	Texas Instruments	Active	Compliant	In Stock	RFQ

Ordering Code Differences

How suffixes on SN74LS map to package, grade, and reel options.

[{"code":"SN74LS00 / 02 / 04 / 08 / 32","meaning":"Common NAND, NOR, inverter, AND, and OR gate functions."},{"code":"SN74LS74 / 138 / 244 / 245","meaning":"Representative flip-flop, decoder, buffer, and transceiver functions."},{"code":"N, D, DB, DW suffixes","meaning":"Package and packing indicators such as PDIP, SOIC, SSOP, or wide SOIC."},{"code":"Open-collector variants","meaning":"Some LS devices depend on pull-up resistors and wired logic behavior; verify output type before substitution."}]

How to Choose the Right SN74LS Buffers, Drivers, Receivers and Transceivers

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Protect TTL loading

Compare input current and fanout before replacing LS logic with CMOS or another TTL family.

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Check output topology

Open-collector, 3-state, and totem-pole outputs are not interchangeable without circuit review.

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Keep timing margins visible

Propagation delay can be part of a legacy timing path, especially in counters and asynchronous logic.

Technical Specifications

Core parameters for SN74LS product family

Logic family

Low-Power Schottky TTL

Nominal supply

5 V class, typically 4.75 V to 5.25 V

Input behavior

TTL thresholds and input current requirements

Common packages

PDIP, SOIC, SOP, SSOP

Typical role

Legacy gates, counters, latches, buffers, and bus logic

Source SN74LS with Octatronics

Request stock confirmation, lead time, date code, and pricing for all 292 ordering variants from Texas Instruments. Our team supports active, EOL, and hard-to-find component sourcing.

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Frequently Asked Questions

Common technical questions about the SN74LS product family.

Can SN74LS be replaced by SN74HC?

Only after checking TTL input levels, input current, output drive, fanout, timing, and output topology. HC CMOS is not an automatic drop-in replacement for LS TTL.

Why are SN74LS parts still sourced?

They are used for repair, long-life industrial equipment, test fixtures, and designs that depend on 5 V TTL electrical behavior.

What is the main difference between LS and HCT logic?

LS is bipolar TTL technology, while HCT is CMOS logic with TTL-compatible inputs. HCT may reduce power, but loading and timing must still be verified.

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