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SN74LS Series DIP-16 Logic ICs – 74LS45 / 219A / 279A / 395A / 169B / 257B / 258B / 259B, Pack of 2

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SN74LS Series DIP-16 Logic ICs — 74LS45 / 219A / 279A / 395A / 169B / 257B / 258B / 259B (2-Pack)

This listing covers the SN74LS series of DIP-16 TTL logic ICs, including BCD decoders, synchronous counters, multiplexers, latches, and shift registers. The 74LS (Low-power Schottky) family operates from 4.75–5.25V and provides the standard TTL logic levels used in legacy digital systems, industrial equipment repair, and electronics education. Select your required variant from the dropdown.

Variant Specifications

Part Number	Function	Description
74LS45	BCD-to-Decimal Decoder/Driver	Decodes 4-bit BCD to 10 active-low outputs, open-collector, 80V/80mA
74LS219A	4×4 RAM (16-bit)	16-bit static RAM, 4-bit address, 4-bit data, open-collector output
74LS279A	Quad S-R Latch	4× SR latches, active-low Set and Reset inputs
74LS395A	4-Bit Shift Register (3-State)	Universal shift register with 3-state outputs and parallel load
74LS169B	4-Bit Synchronous Counter	Up/down binary counter, synchronous load, carry/borrow output
74LS257B	Quad 2-to-1 Mux (3-State)	4× 2-to-1 multiplexer with 3-state outputs, non-inverting
74LS258B	Quad 2-to-1 Mux (3-State, Inverting)	4× 2-to-1 multiplexer with 3-state outputs, inverting
74LS259B	8-Bit Addressable Latch	8-bit latch with 3-bit address select, clear input

Key Specifications (All Variants)

Parameter	Value
Logic Family	74LS (Low-power Schottky TTL)
Package	DIP-16 (through-hole)
Supply Voltage	4.75V – 5.25V (5V nominal)
Input Logic Levels	VIH ≥ 2.0V, VIL ≤ 0.8V (TTL levels)
Propagation Delay	~10–20ns typ.
Operating Temperature	0°C to +70°C (SN74LS) / -40°C to +85°C (SN54LS)
Quantity	2 pieces

74LS vs 74HC — TTL vs CMOS Logic

Feature	74LS (TTL)	74HC (CMOS)
Supply Voltage	5V only	2–6V
Input Levels	TTL (VIH=2.0V)	CMOS (VIH=70% VCC)
Power Consumption	Higher (static current)	Lower (near-zero static)
Output Drive	Higher sink current	Lower sink current
Best For	Legacy TTL system repair, 5V-only systems	New designs, 3.3V/5V systems

Why Choose SN74LS Series?

Legacy TTL compatibility — direct replacement for failed ICs in vintage computers, industrial PLCs, and legacy equipment
TTL input levels — compatible with 5V TTL systems where CMOS HC series may not meet VIH requirements
Open-collector outputs — 74LS45 and 74LS219A open-collector outputs for wired-OR and high-voltage drive
Texas Instruments quality — SN74LS series with comprehensive datasheet support
2-pack value — one for installation, one for spare

Frequently Asked Questions

Q: Can I replace 74LS ICs with 74HC ICs in an existing circuit?
A: Sometimes, but with caution. 74HC has CMOS input thresholds (VIH=70% VCC=3.5V at 5V), while 74LS outputs VOH=2.7V min — which may not reliably drive 74HC inputs. Use 74HCT series instead, which accepts TTL input levels (VIH=2.0V) while providing CMOS output levels. For direct replacement, 74HCT is safer than 74HC.

Q: What is the difference between 74LS169B and 74LS163A?
A: Both are 4-bit synchronous binary counters. 74LS169B counts both up and down (bidirectional) with a direction control pin. 74LS163A counts up only. Use 74LS169B when you need bidirectional counting (e.g., encoder position tracking, frequency synthesis).

Q: How do I use 74LS259B as an 8-output demultiplexer?
A: Connect the 3-bit address (A0–A2) to select one of 8 outputs (Q0–Q7). Apply data to the D input. With ̅C̅L̅R̅ HIGH and ̅E̅ LOW (enable), the selected output follows D while others hold their previous state. This makes it ideal for sequentially addressing 8 output channels from a microcontroller with only 4 pins (A0–A2 + D).