Part A
74HCT08D
도시바 반도체 및 스토리지
- Lifecycle
- Active
- Stock
- 6154 PCS
- Package
- SOIC-14
- Series
- 로직 - 도어 및 인버터
Replacement verdict
Not a drop-in replacement
The 74HCT08D and 74HCT125D-Q100J are not functionally interchangeable. The 74HCT08D provides four 2-input AND gates with push-pull outputs, while the 74HCT125D-Q100J contains four independent non-inverting buffers with 3-state outputs and is qualified to the automotive AEC-Q100 standard. The differing logic function, output structure, and qualification grade prevent direct substitution without circuit redesign.
Different logic function
Different output type
Different enable control
Different qualification grade
Parts at a glance
Part B
74HCT125D-Q100J
넥스페리아 USA 주식회사
- Lifecycle
- Active
- Stock
- 9544 PCS
- Package
- SOIC-14
- Series
- 논리 - 버퍼, 드라이브, 수신기, 트랜시버
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT08D | 74HCT125D-Q100J | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input AND gate | Quad buffer with 3-state outputs | The logic function determines the fundamental operation performed; these parts are not functionally interchangeable. |
| Number of Gates / Buffers | 4 | 4 | Both provide four independent channels, but the channel type differs (AND gate vs. 3-state buffer). |
| Output Type | Push-pull (totem-pole) | 3-state (tri-state) | 3-state outputs allow bus sharing by high-impedance disconnection, while push-pull outputs cannot be tied together. |
| Output Enable Control | None | Yes (active-low OE per channel) | Enable pins allow the output to be placed in high-impedance state, essential for bus-oriented designs. |
| Inputs per Channel | 2 | 1 | AND gates require two inputs to produce a logic output, whereas buffers pass a single input signal. |
| Supply Voltage Range (VCC) | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both operate in the standard HCT 5 V range, so supply compatibility is identical. |
| Propagation Delay (tpd) | ~17 ns (typical at 5 V) | ~14 ns (typical at 5 V) | Propagation delay affects timing margins in synchronous and high-speed digital circuits. |
| Output Drive Current (IOH/IOL) | ±4 mA | ±6 mA | Drive current determines fan-out and ability to drive loads such as LEDs or long traces. |
| Qualification / Grade | Standard commercial | AEC-Q100 automotive qualified | Automotive qualification ensures reliability and compliance for harsh-environment applications. |
| Package | SO14 (SOIC-14) | SO14 (SOIC-14) | Identical package footprint allows PCB layout compatibility, though pin functions differ. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT08D | 74HCT125D-Q100J |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HCT | Automotive, AEC-Q100, 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | AND Gate | Buffer, Non-Inverting |
| Number of Elements | - | 4 |
| Number of Bits per Element | - | 1 |
| Output Type | - | 3-State |
| Current - Output High Low | 4mA, 4mA | 6mA, 6mA |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Circuits | 4 | - |
| Number of Inputs | 2 | - |
| Current - Quiescent (Max) | 1 µA | - |
| Logic Level - Low | 0.8V | - |
| Logic Level - High | 2V | - |
| Max Propagation Delay @ V Max CL | 18ns @ 5.5V, 50pF | - |
Frequently asked questions
What are the primary functional differences between the 74HCT08D and the 74HCT125D-Q100J?
The 74HCT08D contains four independent 2-input AND gates with standard push-pull outputs. The 74HCT125D-Q100J contains four independent non-inverting buffers with 3-state outputs, allowing each buffer to be placed in a high-impedance state via its active-low output enable pin.
Are the 74HCT08D and 74HCT125D-Q100J pin-compatible in the SO14 package?
No. Although both devices are offered in a 14-pin SO package, their pin functions differ. The 74HCT08D uses pins 1, 2, 4, 5, 9, 10, 12, and 13 as gate inputs and pins 3, 6, 8, and 11 as gate outputs. The 74HCT125D-Q100J uses pins 1, 4, 10, and 13 as active-low output enable inputs, pins 2, 5, 9, and 12 as data inputs, and pins 3, 6, 8, and 11 as 3-state outputs. A direct drop-in replacement is therefore not possible without PCB and netlist changes.
Do both devices operate from the same supply voltage range?
Yes. Both the 74HCT08D and the 74HCT125D-Q100J are HCT-family logic devices specified for a nominal 5 V supply, with a recommended operating supply voltage range of 4.5 V to 5.5 V.
What is the difference in output drive capability between the 74HCT08D and the 74HCT125D-Q100J?
Both devices are specified with standard HCT-family output drive of ±4 mA at 5 V. The 74HCT08D provides this drive on its push-pull AND gate outputs, while the 74HCT125D-Q100J provides the same ±4 mA drive on its 3-state buffer outputs when enabled.
Does the 74HCT125D-Q100J have any automotive qualification that the 74HCT08D lacks?
Yes. The 74HCT125D-Q100J carries the Q100 suffix, indicating it is qualified to the AEC-Q100 standard for automotive applications. The 74HCT08D is a standard commercial-grade logic device and is not AEC-Q100 qualified.
Can the 74HCT125D-Q100J be used to replace the 74HCT08D in an AND gate application?
No, not directly. The 74HCT125D-Q100J is a non-inverting 3-state buffer, not an AND gate. Implementing an AND function with the 74HCT125D-Q100J would require additional external logic or a different circuit topology, and the 3-state output behavior would also need to be accounted for in the design.
What are the input threshold and logic level characteristics of these two devices?
Both devices are HCT-family parts, so they feature TTL-compatible input thresholds when operated at 5 V. This allows them to accept TTL-level logic signals while providing CMOS-compatible output levels. The 74HCT08D applies these characteristics to its AND gate inputs, and the 74HCT125D-Q100J applies them to its buffer data inputs and active-low enable inputs.
Which device is more suitable for bus-oriented or multiplexed signal applications?
The 74HCT125D-Q100J is more suitable for bus-oriented applications because its 3-state outputs can be disabled to place the output in a high-impedance state, allowing multiple devices to share a common bus line. The 74HCT08D has standard push-pull outputs and cannot be placed in a high-impedance state, so it is not intended for direct bus sharing.