Part A
74VHC14MX
Компания Fairchild Semiconductor
- Lifecycle
- Active
- Stock
- 3753 ПКС
- Package
- SOIC-14
- Series
- Логика - Ворота и инверторы
Replacement verdict
Not a drop-in replacement
The 74VHC14MX and 74VHC08SJ are not functionally interchangeable despite sharing the same VHC logic family and SOIC-14 footprint. The 74VHC14MX provides six inverting Schmitt-trigger buffers with hysteresis, while the 74VHC08SJ provides four 2-input AND gates with standard CMOS input thresholds. The differing logic function, gate count, and input characteristics make direct substitution impossible without circuit redesign.
Different logic function
Different gate count
Different input threshold
Different output drive
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74VHC14MX | 74VHC08SJ | Why it matters |
|---|---|---|---|
| Logic Function | Hex Inverter with Schmitt Trigger Inputs | Quad 2-Input AND Gate | The logic function determines the fundamental signal operation; these devices perform completely different Boolean functions and are not functionally interchangeable. |
| Number of Gates | 6 | 4 | The gate count affects how many independent signal paths can be processed in a single package, impacting board layout and component count. |
| Number of Inputs per Gate | 1 | 2 | Input count per gate defines the logic capability; a single-input inverter cannot perform a two-input AND function. |
| Schmitt Trigger Inputs | Yes | No | Schmitt trigger inputs provide hysteresis for noise immunity and slow-edge signal conditioning, a feature absent in standard AND gates. |
| Output Type | Inverting | Non-Inverting | Output polarity determines the logic state produced relative to the input, directly affecting circuit behavior. |
| Supply Voltage Range | 2.0 V to 5.5 V | 2.0 V to 5.5 V | The operating voltage range must match the system power rail for reliable logic level translation and compatibility. |
| Propagation Delay (Typical) | 8.5 ns at 5 V | 5.5 ns at 5 V | Propagation delay affects timing margins and maximum operating frequency in synchronous digital circuits. |
| Output Drive Current | ±8 mA | ±8 mA | Output drive current determines the ability to drive loads such as LEDs, transmission lines, or other logic inputs. |
| Package Type | SOIC-14 | SOIC-14 | Package type and pin count affect PCB footprint, thermal characteristics, and assembly compatibility. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | The temperature range ensures reliable operation across the intended environmental conditions of the application. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC14MX | 74VHC08SJ |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74VHC | 74VHC |
| Part Status | Active | Obsolete |
| Logic Type | Inverter | AND Gate |
| Number of Circuits | 6 | 4 |
| Number of Inputs | 1 | 2 |
| Voltage - Supply | 2V ~ 5.5V | 2V ~ 5.5V |
| Current - Quiescent (Max) | 2 µA | 2 µA |
| Current - Output High Low | 8mA, 8mA | 8mA, 8mA |
| Logic Level - Low | 0.9V ~ 1.65V | 0.5V |
| Logic Level - High | 2.2V ~ 3.85V | 1.5V |
| Max Propagation Delay @ V Max CL | 10.6ns @ 5V, 50pF | 7.9ns @ 5V, 50pF |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Features | Schmitt Trigger | - |
Frequently asked questions
What are the primary functional differences between the 74VHC14MX and the 74VHC08SJ?
The 74VHC14MX is a hex Schmitt-trigger inverter, providing six independent inverter gates with hysteresis on the inputs. The 74VHC08SJ is a quad 2-input AND gate, providing four independent AND gates. They perform fundamentally different logic functions and are not functionally equivalent.
Are the 74VHC14MX and 74VHC08SJ pin-to-pin compatible?
No. The 74VHC14MX is typically supplied in an SOIC-14 package with a standard hex inverter pinout, while the 74VHC08SJ is supplied in an SOIC-14 package with a quad 2-input AND gate pinout. Although both may use a 14-pin package, the signal assignments and internal gate configurations differ, so they cannot be interchanged without redesigning the circuit.
Can the 74VHC14MX be used to replace the 74VHC08SJ in an existing design?
No. The 74VHC14MX is an inverting Schmitt-trigger device, while the 74VHC08SJ is a non-inverting AND gate. Replacing one with the other would invert signal polarity and change the logic function, which would cause functional failure in most designs.
Do both devices operate from the same supply voltage range?
Yes. Both the 74VHC14MX and 74VHC08SJ are part of the VHC logic family and are specified for a recommended operating supply voltage range of 2.0 V to 5.5 V, with typical operation at 3.3 V or 5 V.
What is the difference in input threshold behavior between the two devices?
The 74VHC14MX features Schmitt-trigger inputs with defined positive-going and negative-going threshold voltages, providing hysteresis for noise immunity and slow input signals. The 74VHC08SJ has standard CMOS input thresholds without hysteresis, so it requires fast, clean input transitions to avoid oscillation.
Are the output drive characteristics of the 74VHC14MX and 74VHC08SJ the same?
Both devices are VHC-family CMOS logic parts and typically provide symmetrical output drive of approximately ±8 mA at 5 V VCC, subject to the specific manufacturer datasheet. However, the actual output current specification should be verified from the respective manufacturer datasheet for the exact ordering part number.
Which device is better suited for debouncing a mechanical switch?
The 74VHC14MX is better suited for debouncing a mechanical switch because its Schmitt-trigger inputs provide hysteresis, which helps reject noise and slow edge transitions. The 74VHC08SJ lacks hysteresis and is not intended for direct interfacing with slow or noisy mechanical signals.
Can both devices be used in the same logic circuit?
Yes. The 74VHC14MX and 74VHC08SJ can be used together in the same circuit because they belong to the same VHC logic family and share compatible supply voltage and logic level specifications. They serve different logic functions and can complement each other in a mixed-signal or digital design.