Part A
74HCT08D
Компания Toshiba Semiconductor и Storage
- Lifecycle
- Active
- Stock
- 6154 ПКС
- Package
- SOIC-14
- Series
- Логика - Ворота и инверторы
Replacement verdict
Not a drop-in replacement
The 74HCT00D and 74HCT08D 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 74HCT08D contains four 2-input AND gates, producing inverted versus non-inverted logic outputs. Direct substitution would alter circuit logic states and is not recommended without redesign.
Different logic function
Different output polarity
Different truth table
Different Boolean operation
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 | 74HCT08D | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input NAND gate | Quad 2-input AND gate | Defines the Boolean operation performed; NAND and AND are not functionally interchangeable without additional inversion. |
| Number of Gates | 4 | 4 | Indicates how many independent logic gates are available in the package for circuit design. |
| Number of Inputs per Gate | 2 | 2 | Determines the fan-in of each gate and the complexity of logic that can be implemented per gate. |
| Output Type | Push-pull (totem-pole) | Push-pull (totem-pole) | Affects drive capability and whether outputs can be tied together; both are standard CMOS push-pull outputs. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Specifies the operating voltage window; both are 5 V TTL-compatible HCT devices. |
| Propagation Delay (typical) | 9 ns at 5 V | 10 ns at 5 V | Impacts maximum operating frequency and timing margins in synchronous designs. |
| Output Drive Current | ±4 mA | ±4 mA | Determines the load that can be driven directly; identical drive strength supports similar fan-out. |
| Input Threshold Type | TTL-compatible | TTL-compatible | Ensures direct interfacing with TTL logic levels when powered at 5 V. |
| Package | SO14 (SOIC-14) | SO14 (SOIC-14) | Physical footprint and pinout must match for drop-in board compatibility. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Defines the environmental conditions under which the device is guaranteed to function. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT08D | 74HCT00D |
|---|---|---|
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Obsolete |
| Logic Type | AND 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 | 18ns @ 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 74HCT08D?
The 74HCT00D contains four independent 2-input NAND gates, while the 74HCT08D contains four independent 2-input AND 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 in a logic circuit.
Are the 74HCT00D and 74HCT08D 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 74HCT08D in an existing design?
No, not as a direct functional replacement. Although the package and pinout are the same, the 74HCT00D performs NAND logic while the 74HCT08D performs AND logic. The output of a NAND gate is the inverse of an AND gate for the same inputs, so substituting one for the other will invert the logic state and change circuit behavior unless the surrounding design is modified accordingly.
What are the recommended operating conditions for the 74HCT00D and 74HCT08D?
Both devices are specified for operation over a supply voltage range of 4.5 V to 5.5 V, with 5 V being the nominal VCC. The operating ambient temperature range for standard commercial-grade versions is typically -40 °C to +85 °C, and input voltages are TTL-compatible with VIH and VIL thresholds defined in the manufacturer datasheets. Always consult the specific manufacturer datasheet for exact limits and derating information.
Do the 74HCT00D and 74HCT08D have the same propagation delay and drive characteristics?
Both devices are fabricated in HCT CMOS technology and exhibit similar propagation delays and output drive capabilities, typically on the order of several nanoseconds at 5 V and capable of driving standard LSTTL loads. However, exact propagation delay, output current, and power dissipation figures may differ slightly between the two functions and between manufacturers, so the datasheet for the specific device should be consulted for guaranteed AC and DC parameters.
Are the 74HCT00D and 74HCT08D interchangeable in terms of logic family and input compatibility?
Yes, both belong to the 74HCT logic family, which features CMOS construction with TTL-compatible input thresholds. This means both can interface directly with TTL outputs and operate from a 5 V supply while providing CMOS-level noise margins. Their input and output voltage characteristics are essentially equivalent, so the choice between them depends on the required logic function rather than on interface compatibility.
What package type does the "D" suffix indicate for the 74HCT00D and 74HCT08D?
The "D" suffix in both part numbers indicates a SO14 package, which is a 14-pin small-outline integrated circuit package with a 1.27 mm lead pitch. This package is surface-mount and is commonly used in space-constrained PCB designs. Both devices are available in this package, ensuring mechanical compatibility when replacing one with the other on an existing board.
Which device should be selected for an application requiring an active-high output when both inputs are high?
The 74HCT08D should be selected. An AND gate produces a high output only when all inputs are high, which matches the active-high output requirement. The 74HCT00D, being a NAND gate, would produce a low output under the same input conditions, so it would not satisfy the stated logic requirement without additional inversion.