Part A
74HC03D
도시바 반도체 및 스토리지
- Lifecycle
- Active
- Stock
- 3334 PCS
- Package
- SOIC-14
- Series
- 로직 - 도어 및 인버터
Replacement verdict
Not a drop-in replacement
The 74HC08D and 74HC03D are not functionally interchangeable despite sharing the same 74HC CMOS logic family and SOIC-14 package. The 74HC08D provides standard push-pull CMOS outputs, while the 74HC03D features open-drain outputs that require external pull-up resistors for proper logic-high operation. This fundamental output architecture difference, combined with divergent electrical drive characteristics, makes direct substitution inadvisable without circuit redesign.
Different output type
External pull-up may be required
Different drive current
Different logic function
Parts at a glance
Part B
74HC08D
도시바 반도체 및 스토리지
- Lifecycle
- Active
- Stock
- 5927 PCS
- Package
- SOIC-14
- Series
- 로직 - 도어 및 인버터
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC08D | 74HC03D | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input AND gate | Quad 2-input NAND gate | The fundamental logic operation differs, so the two parts are not functionally interchangeable in a circuit. |
| Output Type | Push-pull (totem-pole) CMOS output | Open-drain N-channel output | Open-drain outputs require an external pull-up resistor and allow wired-OR/level-shifting, while push-pull outputs drive both high and low directly. |
| Output Drive Current (IOH/IOL) | ±4 mA (standard HC drive) | -4 mA (low) / no source current (high-Z high state) | Drive capability and the ability to source current differ, affecting fan-out and the need for external pull-ups. |
| High-Level Output Voltage (VOH) | ~VCC (typically 4.4 V at VCC=4.5 V) | Depends on external pull-up; not driven by the device | The AND gate actively drives the output high, whereas the NAND gate relies on an external pull-up to define the high level. |
| Propagation Delay (tPD) | ~9 ns typical at VCC=4.5 V | ~9 ns typical at VCC=4.5 V (with pull-up) | Timing is similar, but the open-drain output's rise time depends on the external pull-up resistor and load capacitance. |
| Supply Voltage Range (VCC) | 2.0 V to 6.0 V | 2.0 V to 6.0 V | Both parts operate over the same supply range, allowing use in similar power environments. |
| Input Voltage Range | 0 V to VCC | 0 V to VCC | Identical input voltage compatibility ensures both can interface with the same logic levels. |
| Package | SO14 (D suffix) | SO14 (D suffix) | Same package and pin count allow drop-in PCB footprint compatibility, though pin functions differ. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Identical temperature ratings suit both parts for the same industrial and automotive environments. |
| Pin Count | 14 | 14 | Same pin count, but pin assignments and functions differ between the AND and NAND configurations. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC03D | 74HC08D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | NAND Gate | AND Gate |
| Number of Circuits | 4 | 4 |
| Number of Inputs | 2 | 2 |
| Features | Open Drain | - |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Current - Quiescent (Max) | 1 µA | 1 µA |
| Current - Output High Low | -, 5.2mA | 5.2mA, 5.2mA |
| Logic Level - Low | 0.5V ~ 1.8V | 0.5V ~ 1.8V |
| Logic Level - High | 1.5V ~ 4.2V | 1.5V ~ 4.2V |
| Max Propagation Delay @ V Max CL | 13ns @ 6V, 50pF | 13ns @ 6V, 50pF |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What is the main functional difference between the 74HC08D and the 74HC03D?
The 74HC08D contains four independent 2-input AND gates with standard push-pull CMOS outputs, while the 74HC03D contains four independent 2-input NAND gates with open-drain outputs. The 74HC03D requires external pull-up resistors to define the high logic level.
Are the 74HC08D and 74HC03D pin-compatible in the SO14 package?
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. This common pinout allows a board designed for one function to be reworked for the other, provided the output-stage differences are accommodated.
Can the 74HC03D directly replace the 74HC08D in an existing design?
Not without design changes. The 74HC08D provides active-high AND logic with a push-pull output that actively drives both high and low levels. The 74HC03D provides active-low NAND logic with an open-drain output that can only pull low and requires an external pull-up resistor for the high state. Logic polarity, output drive, and external component requirements must all be re-evaluated.
What are the output drive capabilities of the 74HC08D and 74HC03D?
Both devices are specified with a standard HC-family output drive of ±4 mA at 5 V VCC. The 74HC08D sources and sinks current in both logic states, whereas the 74HC03D only sinks current when pulling low; the high level is established by the external pull-up resistor and the connected load.
What supply voltage range do the 74HC08D and 74HC03D support?
Both devices operate over a supply voltage range of 2.0 V to 6.0 V, which is the standard operating range for the 74HC logic family. Parametric limits such as propagation delay, input threshold, and output drive vary with the applied VCC within this range.
Why does the 74HC03D require a pull-up resistor while the 74HC08D does not?
The 74HC03D has an open-drain output stage, meaning its output transistor can only connect the output to ground. When the output is off, the node floats unless an external pull-up resistor connects it to VCC. The 74HC08D has a push-pull output stage that actively drives the output both high and low, so no external pull-up is required for normal logic operation.
Can the 74HC03D be used for wired-OR or wired-AND configurations?
Yes. Because the 74HC03D has open-drain outputs, multiple outputs can be tied together with a single pull-up resistor to implement a wired-AND (active-low wired-OR) function. The 74HC08D cannot be used this way because its push-pull outputs would contend if connected together.
Are the 74HC08D and 74HC03D interchangeable in mixed-voltage or level-shifting applications?
They are not directly interchangeable for level shifting. The 74HC03D open-drain output can be pulled up to a voltage different from its own VCC, which allows it to interface with a higher-voltage logic rail within the device's absolute maximum ratings. The 74HC08D push-pull output is referenced to its own VCC and cannot directly drive a rail above VCC.