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74HCT125D

Quad buffer/line driver, 3-state, HCT, SOIC-14, 13ns, LSTTL compatible, bus driver

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Manufacturer Part：

74HCT125D

Package：

SOIC-14 (8.65 x 3.91 x 1.58 mm)

Description

Product Overview

The 74HCT125D from Nexperia is a quad buffer/line driver with 3-state outputs in SOIC-14. Each buffer has an active-low output enable, allowing bus-oriented applications where multiple devices share common data lines. HCT input levels provide compatibility with LSTTL while driving CMOS-level outputs.

Key Specifications

Logic Family	74HCT
Supply Voltage	4.5 V to 5.5 V
Propagation Delay	13 ns (typ)
Output Current	+/-6 mA
Input Levels	LSTTL compatible (HCT)
Channels	4 (independent)
Output Enable	Active low (per buffer)
Operating Temperature	-40C to +125C

Features

Quad non-inverting buffer with individual 3-state output enables
HCT input compatibility with LSTTL logic levels
Active-low output enable per channel for bus sharing
13ns typical propagation delay for fast signal buffering

Applications

Bus driver and buffer for microprocessor systems
3-state bus interface for shared data lines
Level translation between TTL and CMOS
Signal buffering and fan-out enhancement

Product Introduction:74HCT125D Product Introduction

The 74HCT125D from Nexperia is a quad non-inverting buffer/line driver with 3-state outputs in SOIC-14. Each of the four buffers has an independent active-low output enable (OE), allowing individual channel control for bus-oriented applications. The HCT input logic levels are compatible with LSTTL (VIH=2.0V, VIL=0.8V) while the outputs drive full CMOS levels at VCC. The device operates from 4.5V to 5.5V with 13ns typical propagation delay and +/-6mA output drive current. When OE is high, the output enters high-impedance state, allowing bus sharing with other devices.

Working Principle:74HCT125D Working Principle

The 74HCT125D contains four independent non-inverting buffers with 3-state output control. (1) Buffer: Each buffer passes the input data to the output without inversion. The HCT input stage has TTL-compatible threshold (VIH=2.0V, VIL=0.8V), enabling direct interface with LSTTL outputs. The output stage drives full CMOS voltage levels. (2) 3-State Control: When the output enable (OE) pin is low, the buffer output is active and drives the data. When OE is high, both the pull-up and pull-down transistors in the output stage are turned off, placing the output in a high-impedance (Hi-Z) state. This allows multiple 3-state devices to share a common bus without contention. (3) Bus Sharing: Only one device should drive the bus at a time. The 13ns propagation delay and fast enable/disable times allow efficient bus arbitration.

Pin Description:74HCT125D Pin Definition and Functions

Pin	Name	Type	Function
1	1OE	Input	Channel A output enable (active low)
2	1A	Input	Channel A data input
3	1Y	Output	Channel A output (3-state)
4	2OE	Input	Channel B output enable (active low)
5	2A	Input	Channel B data input
6	2Y	Output	Channel B output (3-state)
7	GND	Ground	Ground
8-14	3Y/3A/3OE/4Y/4A/4OE/VCC	I/O	Channels C, D, and power

Application Scenarios:In which products and applications is74HCT125D used

Microprocessor bus driver with 3-state output for shared data lines
Level translation between TTL outputs and CMOS inputs
Signal buffering and fan-out enhancement for clock and control signals
I/O port expansion with individual enable control

Alternative Models:What chips are recommended as replacements for 74HCT125D

Manufacturer	Part Number	Package	Notes
TI	SN74HCT125DR	SOIC-14	Direct equivalent
onsemi	MC74HCT125ADG	SOIC-14	Direct equivalent
Nexperia	74HC125D	SOIC-14	HC version, CMOS inputs
Nexperia	74HCT126D	SOIC-14	Active-high enable version