Part A
74HCT02D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 5658 Stückzahl
- Package
- SOIC-16
- Series
- Logic-Gates und Wechselrichter
Replacement verdict
Not a drop-in replacement
The 74HCT14D and 74HCT02D are not functionally interchangeable despite sharing the same 74HCT logic family and SOIC-14 package. The 74HCT14D provides six inverting Schmitt-trigger buffers with hysteresis, while the 74HCT02D contains four 2-input NOR gates with standard CMOS input thresholds. Their differing logic functions, gate counts, input characteristics, and output drive capabilities make direct substitution impossible without circuit redesign.
Different logic function
Different gate count
Different input threshold
Different output drive
Parts at a glance
Part B
74HCT14D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 6342 Stückzahl
- Package
- SOIC-14
- Series
- Logic-Gates und Wechselrichter
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT14D | 74HCT02D | Why it matters |
|---|---|---|---|
| Logic Function | Hex inverting Schmitt trigger | Quad 2-input NOR gate | Defines the fundamental logic operation; these devices are not functionally interchangeable. |
| Number of Gates/Channels | 6 | 4 | Determines how many independent signal paths are available in a single package. |
| Number of Inputs per Gate | 1 | 2 | Affects the logic complexity each gate can implement and the required input wiring. |
| Input Type | Schmitt trigger | Standard CMOS/TTL-compatible | Schmitt trigger inputs provide hysteresis for noise immunity and slow signal edges, which standard inputs lack. |
| Output Type | Inverting | Inverting (NOR) | Determines the logic polarity of the output relative to the inputs. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Defines the compatible power supply window for proper HCT-family operation. |
| Logic Family | HCT | HCT | Ensures TTL-compatible input thresholds and similar drive characteristics. |
| Package | SO14 | SO14 | Same package footprint allows drop-in board placement compatibility. |
| Mounting Type | Surface mount | Surface mount | Confirms both parts are suitable for the same assembly process. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Ensures both devices can operate reliably in the same environmental conditions. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT02D | 74HCT14D |
|---|---|---|
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | NOR Gate | Inverter |
| Number of Circuits | 4 | 6 |
| Number of Inputs | 2 | 1 |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Current - Quiescent (Max) | 1 µA | 1 µA |
| Current - Output High Low | 4mA, 4mA | 4mA, 4mA |
| Logic Level - Low | 0.8V | - |
| Logic Level - High | 2V | - |
| Max Propagation Delay @ V Max CL | 16ns @ 5.5V, 50pF | 31ns @ 5.5V, 50pF |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Features | - | Schmitt Trigger |
Frequently asked questions
What are the primary functional differences between the 74HCT14D and the 74HCT02D?
The 74HCT14D contains six independent Schmitt-trigger inverters, providing hysteresis for slow or noisy input signals. The 74HCT02D contains four independent 2-input NOR gates without Schmitt-trigger inputs. They are not functionally equivalent and cannot be used interchangeably without redesigning the surrounding circuit.
Are the 74HCT14D and 74HCT02D pin-compatible in the SO14 package?
No. Although both devices are commonly offered in a 14-pin SO package, their pinouts differ. The 74HCT14D assigns six inverter inputs and six outputs across the 14 pins with VCC and GND, while the 74HCT02D assigns four 2-input NOR gates with a different input/output arrangement. Direct PCB substitution is not possible.
Do both devices operate from the same supply voltage range?
Yes. Both the 74HCT14D and 74HCT02D are HCT-family logic devices specified for a nominal 5 V supply with a recommended operating range of 4.5 V to 5.5 V, and they are TTL-voltage compatible at their inputs.
Does the 74HCT02D have Schmitt-trigger inputs like the 74HCT14D?
No. The 74HCT02D has standard CMOS/TTL-compatible inputs without Schmitt-trigger hysteresis. Only the 74HCT14D provides Schmitt-trigger inputs with defined positive and negative threshold voltages, which makes it suitable for signal conditioning and debouncing applications.
Can the 74HCT14D be used to replace the 74HCT02D in a NOR gate application?
No. An inverter cannot perform the logical NOR function of two inputs. Replacing a 74HCT02D with a 74HCT14D would require additional logic gates and a redesigned circuit; the two devices implement different Boolean functions and are not drop-in replacements.
What are the typical propagation delays for these devices?
Both are HCT-family devices with propagation delays typically in the low nanosecond range at 5 V. Exact tPD values depend on the specific manufacturer, load capacitance, and test conditions, so the datasheet for the exact part number and vendor should be consulted for guaranteed limits.
Are the 74HCT14D and 74HCT02D available in the same package options?
Both are widely available in SO14 surface-mount packages and in DIP-14 through-hole packages from multiple manufacturers. Package availability can vary by vendor, so the specific orderable part number and its datasheet should be checked before design release.
Which device is better for debouncing a mechanical switch?
The 74HCT14D is the appropriate choice because its Schmitt-trigger inputs provide hysteresis that cleanly squares up slow or noisy edges from mechanical switches. The 74HCT02D lacks hysteresis and is not intended for direct switch debouncing without external circuitry.