Part A
74HCT02D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 5658 PCS
- Package
- SOIC-16
- Series
- Logique - portes et Onduleurs
Replacement verdict
Not a drop-in replacement
The 74HCT00D and 74HCT02D are not functionally interchangeable despite sharing the same 74HCT logic family, SO14 package, and supply voltage range. The 74HCT00D contains four 2-input NAND gates, while the 74HCT02D contains four 2-input NOR gates, producing inverted logic functions that cannot be substituted without redesigning the surrounding circuit. Pin assignments also differ between the two devices, so a direct board-level swap is not possible.
Different logic function
Different pin assignment
Different truth table
Different gate topology
Parts at a glance
Part B
74HCT00D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 1289 PCS
- Package
- SOIC-20
- Series
- Logique - portes et Onduleurs
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT00D | 74HCT02D | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input NAND gate | Quad 2-input NOR gate | The logic function determines the boolean operation performed; NAND and NOR are not functionally interchangeable in a circuit. |
| Logic Family | HCT (High-speed CMOS, TTL-compatible) | HCT (High-speed CMOS, TTL-compatible) | Same logic family ensures compatible input thresholds and output drive characteristics. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both devices operate from the same nominal 5 V supply with identical tolerance, allowing direct substitution in the power domain. |
| Number of Gates | 4 | 4 | Matching gate count ensures the same number of logic operations can be implemented per package. |
| Number of Inputs per Gate | 2 | 2 | Identical input count per gate preserves the fan-in requirements of the original design. |
| Package | SO14 (SOIC-14) | SO14 (SOIC-14) | Same package and pin count allow drop-in PCB footprint compatibility. |
| Propagation Delay (typical) | 9 ns at 5 V | 9 ns at 5 V | Similar propagation delay ensures comparable timing behavior in the target circuit. |
| Output Drive Current | ±4 mA | ±4 mA | Matching output drive capability ensures equivalent fan-out and load driving performance. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Identical temperature range ensures both parts are suitable for the same environmental conditions. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT02D | 74HCT00D |
|---|---|---|
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Obsolete |
| Logic Type | NOR Gate | NAND Gate |
| Number of Circuits | 4 | 4 |
| Number of Inputs | 2 | 2 |
| 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 | 0.8V |
| Logic Level - High | 2V | 2V |
| Max Propagation Delay @ V Max CL | 16ns @ 5.5V, 50pF | 17ns @ 5.5V, 50pF |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary functional differences between the 74HCT00D and 74HCT02D?
The 74HCT00D contains four independent 2-input NAND gates, while the 74HCT02D contains four independent 2-input NOR gates. Both are members of the 74HCT CMOS logic family with TTL-compatible inputs, but they implement different Boolean functions and therefore are not functionally interchangeable.
Are the 74HCT00D and 74HCT02D pin-compatible?
Yes. Both devices are offered in the SO14 (D) package and use the same 14-pin pinout: pins 1, 2, 4, 5, 9, 10, 12, and 13 are gate inputs, pins 3, 6, 8, and 11 are gate outputs, pin 7 is GND, and pin 14 is VCC. Because the pinout is identical, a board designed for one device can physically accept the other, but the logic function performed at each gate position will differ.
Can the 74HCT00D be used as a drop-in replacement for the 74HCT02D in an existing design?
No, not as a direct functional replacement. Although both devices share the same SO14 package and pinout, the 74HCT00D provides NAND functions while the 74HCT02D provides NOR functions. Substituting one for the other will change the logic behavior of the circuit unless the surrounding design is modified to compensate for the different Boolean function.
What are the recommended operating supply voltage and logic level specifications for both devices?
Both the 74HCT00D and 74HCT02D are specified for operation from 4.5 V to 5.5 V, with 5 V as the nominal supply. As HCT-family devices, they feature TTL-compatible input thresholds (VIH minimum of 2.0 V and VIL maximum of 0.8 V at 5 V), allowing direct interfacing with TTL logic while retaining CMOS output drive characteristics.
Do the 74HCT00D and 74HCT02D have the same propagation delay and output drive characteristics?
Both devices are members of the same 74HCT logic family and are specified with comparable propagation delays and output drive currents in their respective manufacturer datasheets. However, exact timing and drive parameters can vary between manufacturers and between the NAND and NOR gate implementations. Designers should consult the specific manufacturer datasheet for the exact device being used rather than assuming identical AC and DC characteristics.
What is the difference between the NAND function of the 74HCT00D and the NOR function of the 74HCT02D?
The 74HCT00D NAND gate outputs a logic LOW only when both inputs are HIGH; for all other input combinations the output is HIGH. The 74HCT02D NOR gate outputs a logic HIGH only when both inputs are LOW; for all other input combinations the output is LOW. These are complementary in structure but produce different truth tables and therefore different logic behavior in a circuit.
Are the 74HCT00D and 74HCT02D available in the same package options?
Both devices are commonly available in the SO14 (D) surface-mount package, which is the package indicated by the "D" suffix in their part numbers. Manufacturers may also offer these functions in other packages such as TSSOP or DIP, but the specific "D" variants referenced here are the SO14 versions. Package availability should be confirmed against the manufacturer's current datasheet and distributor listing.
Which applications typically use the 74HCT00D versus the 74HCT02D?
The 74HCT00D is commonly used for NAND-based logic functions such as signal gating, flip-flop construction, oscillator circuits, and general combinational logic. The 74HCT02D is commonly used for NOR-based functions such as set-reset latches, enable/disable control logic, and combinational logic where a HIGH output is required only when all inputs are LOW. The choice between them depends on the required Boolean function in the target circuit.