Part A
74HC123D
NXP USA Inc.
- Lifecycle
- Active
- Stock
- 3320 PCS
- Package
- SOIC-16
- Series
- Logique - multivibrateurs
Replacement verdict
Not a drop-in replacement
The 74HC125D and 74HC123D are not functionally interchangeable despite sharing the same 74HC logic family and SOIC-14 package. The 74HC125D is a quad bus buffer with 3-state outputs, while the 74HC123D is a dual retriggerable monostable multivibrator. Their core logic functions, pinout assignments, and output behavior differ fundamentally, making direct substitution impossible without circuit redesign.
Different logic function
Different output type
Different pinout
Different channel count
Parts at a glance
Part B
74HC125D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 3803 PCS
- Package
- SOIC-14
- Series
- Logique - Buffers, lecteurs, récepteurs, émetteurs - récepteurs
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC125D | 74HC123D | Why it matters |
|---|---|---|---|
| Logic Function | Quad Buffer/Line Driver with 3-State Outputs | Dual Retriggerable Monostable Multivibrator | These devices perform fundamentally different logic functions, so they are not functionally substitutable in a circuit. |
| Number of Channels | 4 | 2 | Channel count determines how many independent signal paths can be handled by a single package. |
| Output Type | 3-State | Push-Pull (Standard CMOS) | 3-state outputs allow bus sharing, while standard outputs cannot be tied together without contention. |
| Primary Function | Signal buffering and bus driving | Pulse generation and timing | The intended application differs completely, affecting whether the part can replace the other in a design. |
| External Timing Components Required | No | Yes (R and C for each monostable) | The monostable requires external RC components to set pulse width, while the buffer does not need them. |
| Control Inputs | Output Enable (active LOW) per channel | Trigger inputs (A, B) and Reset per channel | Different control schemes mean the surrounding circuitry and signal timing must be redesigned. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both parts operate over the same HC-family supply range, so power supply compatibility is not a differentiator. |
| Package | SO14 (D package) | SO16 (D package) | Package footprint and pin count affect PCB layout and whether a direct drop-in replacement is possible. |
| Propagation Delay (typical) | Approximately 10 ns at 4.5 V | Approximately 25 ns at 4.5 V (trigger to output) | Timing performance influences maximum operating frequency and signal integrity in high-speed designs. |
| Pin Count | 14 | 16 | Different pin counts prevent pin-to-pin compatibility on the same PCB footprint. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC123D | 74HC125D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | Monostable | Buffer, Non-Inverting |
| Independent Circuits | 2 | - |
| Schmitt Trigger Input | Yes | - |
| Propagation Delay | 40 ns | - |
| Current - Output High Low | 5.2mA, 5.2mA | 7.8mA, 7.8mA |
| Voltage - Supply | 2 V ~ 6 V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Elements | - | 4 |
| Number of Bits per Element | - | 1 |
| Output Type | - | 3-State |
Frequently asked questions
What are the primary functions of the 74HC125D and 74HC123D?
The 74HC125D is a quad non-inverting 3-state buffer/line driver with active-low output enable pins. The 74HC123D is a dual retriggerable monostable multivibrator with reset, used for pulse generation and timing applications.
Can the 74HC125D and 74HC123D be used interchangeably in a circuit?
No. The 74HC125D is a logic buffer/line driver, while the 74HC123D is a monostable multivibrator. They perform fundamentally different functions and are not pin-to-pin or functionally interchangeable.
Do the 74HC125D and 74HC123D share the same package and pinout?
Both devices are commonly offered in a 16-pin SOIC package (D suffix). However, their pinouts differ because the 74HC125D has four buffers with individual enable pins, while the 74HC123D has two monostable multivibrators with timing, trigger, and reset pins.
What are the typical supply voltage ranges for the 74HC125D and 74HC123D?
Both devices are 74HC series CMOS logic and typically operate from 2.0 V to 6.0 V. Always verify the exact limits in the manufacturer datasheet for the specific part number.
Which device is suitable for driving a bus or transmission line?
The 74HC125D is suitable for bus driving because it provides 3-state outputs that can be placed in a high-impedance state, allowing multiple devices to share a common bus. The 74HC123D is not intended for bus driving.
Which device is used for pulse stretching or timing applications?
The 74HC123D is used for pulse stretching, timing, and monostable multivibrator functions. It produces an output pulse of a defined width set by external resistor and capacitor values. The 74HC125D does not provide timing functions.
Are the 74HC125D and 74HC123D available in the same logic family?
Yes. Both are members of the 74HC high-speed CMOS logic family, which provides CMOS low power consumption with TTL-compatible input thresholds when operated at 5 V.
What is the key difference in output behavior between the 74HC125D and 74HC123D?
The 74HC125D output follows the input logic level when enabled and enters high impedance when disabled. The 74HC123D output generates a single pulse of determined width when triggered, independent of the input pulse width after triggering.