Part A
74HCT00D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 1289 PCS
- Package
- SOIC-20
- Series
- Logique - portes et Onduleurs
Replacement verdict
Not a drop-in replacement
The 74HCT00D and 74HCT240D are not functionally interchangeable despite sharing the same 74HCT logic family and SOIC-14 package. The 74HCT00D is a quad 2-input NAND gate, while the 74HCT240D is an octal 3-state inverting buffer. Their logic functions, channel counts, output drive configurations, and pinouts differ fundamentally, so substituting one for the other is not possible without redesigning the surrounding circuit.
Different logic function
Different channel count
Different output type
Different pinout
Parts at a glance
Part B
74HCT240D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 7637 PCS
- Package
- SOIC-20
- Series
- Logique - Buffers, lecteurs, récepteurs, émetteurs - récepteurs
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 | 74HCT240D | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input NAND gate | Octal 3-state inverting buffer/line driver | Defines the fundamental logic operation performed; these devices are not functionally interchangeable. |
| Number of Gates / Channels | 4 gates | 8 buffers | Determines how many independent signal paths the device can process. |
| Output Type | Push-pull (totem-pole) | 3-state (tri-state) inverting | 3-state outputs allow bus sharing; push-pull outputs cannot be tied together. |
| Number of Pins | 14 | 20 | Different package pin counts mean different footprints and are not drop-in compatible. |
| Package | SO14 (SOIC-14) | SO20 (SOIC-20) | Physical package determines PCB footprint and assembly compatibility. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both operate from standard 5 V TTL-compatible supply rails. |
| Logic Family | HCT (High-speed CMOS, TTL-compatible) | HCT (High-speed CMOS, TTL-compatible) | Same logic family ensures compatible input thresholds and output levels. |
| Propagation Delay (typical) | ~9 ns at 5 V | ~12 ns at 5 V | Affects maximum operating frequency and timing margins in a circuit. |
| Output Drive Current | ±4 mA | ±6 mA | Determines fan-out capability and ability to drive loads or other logic inputs. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Both support industrial temperature ranges for harsh environments. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT00D | 74HCT240D |
|---|---|---|
| Supplier | - | Toshiba Semiconductor and Storage |
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | NAND Gate | Buffer, Inverting |
| Number of Elements | - | 2 |
| Number of Bits per Element | - | 4 |
| Output Type | - | 3-State |
| Current - Output High Low | 4mA, 4mA | 6mA, 6mA |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Circuits | 4 | - |
| Number of Inputs | 2 | - |
| Current - Quiescent (Max) | 1 µA | - |
| Logic Level - Low | 0.8V | - |
| Logic Level - High | 2V | - |
| Max Propagation Delay @ V Max CL | 17ns @ 5.5V, 50pF | - |
Frequently asked questions
What are the primary functional differences between the 74HCT00D and the 74HCT240D?
The 74HCT00D contains four independent 2-input NAND gates, while the 74HCT240D contains eight independent 3-state inverting buffers arranged as two 4-bit groups. The 74HCT00D performs logic gating, whereas the 74HCT240D is designed for bus driving and signal buffering with high-impedance output capability.
Are the 74HCT00D and 74HCT240D pin-compatible?
No. The 74HCT00D is typically supplied in a 14-pin SOIC package, while the 74HCT240D is typically supplied in a 20-pin SOIC package. They have different pin counts, pin assignments, and functions, so they are not pin-compatible or directly interchangeable.
Can the 74HCT00D and 74HCT240D operate from the same supply voltage?
Yes. Both devices are members of the 74HCT logic family and are specified for a nominal 5 V supply with an operating range typically from 4.5 V to 5.5 V, as stated in standard 74HCT datasheets.
Does the 74HCT240D have 3-state outputs while the 74HCT00D does not?
Yes. The 74HCT240D features 3-state outputs controlled by two active-low output enable pins, allowing its outputs to be placed in a high-impedance state for bus sharing. The 74HCT00D has standard totem-pole outputs without 3-state capability.
Which device is more suitable for driving a shared data bus?
The 74HCT240D is more suitable because its 3-state outputs permit multiple devices to share a common bus without contention. The 74HCT00D lacks 3-state outputs and is intended for fixed logic functions rather than bus interfacing.
Do both devices provide the same output drive current?
No. The 74HCT240D is specified with higher output drive capability, typically ±6 mA per output, to support bus driving. The 74HCT00D typically provides ±4 mA output drive. Exact values should be confirmed from the specific manufacturer datasheet.
Can the 74HCT00D be used to replace the 74HCT240D in an existing design?
No. The two devices differ in logic function, pin count, package, and output type. A direct replacement is not possible without redesigning the circuit to accommodate the different functionality and pinout.
Are both the 74HCT00D and 74HCT240D available in SOIC packages?
Yes. Both devices are commonly offered in SOIC packages, but with different pin counts: the 74HCT00D in a 14-pin SOIC and the 74HCT240D in a 20-pin SOIC. Package suffix "D" generally denotes SOIC in many manufacturer naming conventions.