Part A
74HCT14D
東芝電晶體與存儲
- Lifecycle
- Active
- Stock
- 6342 件
- Package
- SOIC-14
- Series
- 邏輯-門和逆變器
Replacement verdict
Not a drop-in replacement
The 74HCT245D and 74HCT14D are not functionally interchangeable despite sharing the 74HCT logic family and SOIC-14 package. The 74HCT245D is an octal bidirectional bus transceiver with three-state outputs and direction control, while the 74HCT14D is a hex inverting Schmitt trigger designed for signal conditioning with hysteresis. Their logic functions, channel counts, pinouts, and output structures differ fundamentally, so substituting one for the other is not feasible without redesigning the surrounding circuit.
Different logic function
Different channel count
Different output type
Different pinout
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT245D | 74HCT14D | Why it matters |
|---|---|---|---|
| Logic Function | Octal bus transceiver, 3-state | Hex inverting Schmitt trigger | The core logic function determines whether the devices are functionally interchangeable; these are fundamentally different functions and cannot substitute for each other. |
| Number of Channels | 8 | 6 | Channel count affects how many signal lines can be handled per package, impacting board layout and I/O capacity. |
| Direction Control | Bidirectional with DIR pin and OE | Unidirectional | Bidirectional capability with direction and output-enable control is essential for bus interfacing, which the Schmitt trigger inverter does not provide. |
| Output Type | 3-state | Push-pull | 3-state outputs allow bus sharing by high-impedance disconnection, while push-pull outputs are always driven. |
| Input Threshold | Standard HCT TTL-compatible | Schmitt trigger with hysteresis | Schmitt trigger hysteresis provides noise immunity for slow or noisy signals, which the standard buffer input lacks. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both operate from the same 5 V nominal HCT supply range, so power supply compatibility is identical. |
| Logic Family | HCT (TTL-compatible CMOS) | HCT (TTL-compatible CMOS) | Same logic family ensures compatible input/output voltage levels with TTL systems. |
| Package | SO16 (D) | SO14 (D) | Package footprint and pin count differ, affecting PCB layout and mechanical compatibility. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Identical temperature ratings mean both suit the same industrial and automotive-grade environments. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT14D | 74HCT245D |
|---|---|---|
| Series | 74HCT | 74HCT |
| Part Status | Active | Active |
| Logic Type | Inverter | Transceiver, Non-Inverting |
| Number of Circuits | 6 | - |
| Number of Inputs | 1 | - |
| Features | Schmitt Trigger | - |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Current - Quiescent (Max) | 1 µA | - |
| Current - Output High Low | 4mA, 4mA | 6mA, 6mA |
| Max Propagation Delay @ V Max CL | 31ns @ 5.5V, 50pF | - |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
| Output Type | - | 3-State |
Frequently asked questions
What are the primary functional differences between the 74HCT245D and the 74HCT14D?
The 74HCT245D is an octal bus transceiver with 3-state outputs, designed for bidirectional asynchronous communication between data buses. The 74HCT14D is a hex inverting Schmitt trigger, used for signal conditioning and waveform shaping of noisy or slow input signals. They serve entirely different logic functions and are not interchangeable.
Can the 74HCT245D and 74HCT14D be used in the same circuit?
Yes, they can coexist in the same circuit because both are members of the 74HCT logic family and operate from a 4.5 V to 5.5 V supply. However, they perform different roles: the 74HCT245D handles bidirectional bus interfacing, while the 74HCT14D provides Schmitt-trigger input hysteresis for noise immunity.
Do the 74HCT245D and 74HCT14D have the same pin count and package?
Both devices are commonly offered in a 14-pin SOIC package (the "D" suffix in the part number typically denotes SOIC). The 74HCT245D uses all 14 pins for its octal transceiver function, while the 74HCT14D uses the same 14-pin package for its hex inverter function. Pinouts are not compatible, so they cannot be swapped on the same PCB footprint.
What are the key electrical characteristics of the 74HCT245D?
The 74HCT245D features TTL-compatible inputs, a wide supply voltage range of 4.5 V to 5.5 V, and 3-state outputs for bus-oriented applications. It provides non-inverting bidirectional data transfer with direction and output-enable controls. Propagation delay and output drive are specified in the manufacturer datasheet.
What are the key electrical characteristics of the 74HCT14D?
The 74HCT14D provides six independent inverting Schmitt-trigger circuits with defined positive and negative input threshold voltages (hysteresis). It operates from 4.5 V to 5.5 V, has TTL-compatible inputs, and is specified for slow input rise and fall times. Exact hysteresis and propagation delay values are provided in the manufacturer datasheet.
Are the 74HCT245D and 74HCT14D drop-in replacements for each other?
No. They have different logic functions, different pinouts, and different internal circuitry. The 74HCT245D is an octal bus transceiver, while the 74HCT14D is a hex Schmitt-trigger inverter. Substituting one for the other without redesigning the circuit will result in incorrect operation.
Which device is better for cleaning up noisy digital signals?
The 74HCT14D is the appropriate choice for cleaning up noisy or slow digital signals because its Schmitt-trigger inputs provide hysteresis, which improves noise immunity and ensures clean output transitions. The 74HCT245D does not have Schmitt-trigger inputs and is not intended for signal conditioning.
Which device is better for bidirectional data bus interfacing?
The 74HCT245D is designed specifically for bidirectional data bus interfacing, offering octal transceivers with 3-state outputs and direction control. The 74HCT14D cannot perform bus transceiver functions because it is a fixed inverting Schmitt-trigger device with no 3-state or direction-control capability.