7421
7421 Dual 4-Input AND Gate - Technical Summary
Overview
The 7421 is a dual 4-input AND gate integrated circuit (IC) belonging to the 7400 series of TTL logic devices. This component contains two independent AND gates, each with four inputs and one output. The 7421 is designed for general-purpose logic operations in digital circuits, providing reliable Boolean logic functionality. It operates within standard TTL voltage levels and is widely used in computing, control systems, and digital signal processing applications.
The device features a robust design with standard pin configurations, making it compatible with existing TTL-based circuit layouts. Its truth table follows standard AND gate logic, where the output is HIGH only when all inputs are HIGH. The 7421 is available in various package options, including DIP (Dual In-line Package) and surface-mount variants.
Features
- Dual 4-Input AND Gates: Contains two independent AND gates in a single package
- Standard TTL Compatibility: Operates with 5V supply voltage
- Wide Operating Voltage Range: 4.75V to 5.25V
- High Noise Immunity: Typical noise margin of 0.4V
- Fast Propagation Delay: Typical tPD of 10ns
- Low Power Consumption: Typical ICC of 4mA per gate
- Standard Pin Configuration: Compatible with existing TTL layouts
- Multiple Package Options: Available in PDIP, SOIC, and other packages
Applications
The 7421 finds application in various digital systems requiring logical AND operations with multiple inputs:
- Digital Logic Circuits: Used in processor control units and ALUs
- Data Processing Systems: For implementing Boolean logic functions
- Control Systems: In industrial automation and process control
- Signal Routing: For gating and enabling signals in communication systems
- Test Equipment: In digital test patterns and signal generation
- Educational Projects: For teaching digital logic fundamentals
Electrical Characteristics
Absolute Maximum Ratings
- Supply Voltage (VCC): -0.5V to +7V
- DC Input Voltage (VI): -0.5V to VCC + 0.5V
- DC Output Voltage (VO): -0.5V to VCC + 0.5V
- DC Input Diode Current (IIK): ±20mA
- Operating Temperature Range: 0°C to 70°C (commercial grade)
Recommended Operating Conditions
- Supply Voltage (VCC): 4.75V to 5.25V
- Input High Voltage (VIH): 2V min
- Input Low Voltage (VIL): 0.8V max
- Output High Current (IOH): -400μA max
- Output Low Current (IOL): 16mA max
DC Characteristics
- Input Clamp Voltage (VIK): -1.5V max at IIK = -18mA
- High Level Output Voltage (VOH): 2.4V min at VCC = min, IOH = max
- Low Level Output Voltage (VOL): 0.4V max at VCC = min, IOL = max
- Input Current (II): ±1μA max at VCC = max, VI = 5.5V
Pin Description
| Pin No. | Symbol | Name and Function |
|---|---|---|
| 1, 9 | 1A to 2A | Data Inputs (First input for each AND gate) |
| 2, 10 | 1B to 2B | Data Inputs (Second input for each AND gate) |
| 3, 11 | NC | Not Connected (No internal connection) |
| 4, 12 | 1C to 2C | Data Inputs (Third input for each AND gate) |
| 5, 13 | 1D to 2D | Data Inputs (Fourth input for each AND gate) |
| 6, 8 | 1Y to 2Y | Data Outputs (Output for each AND gate) |
| 7 | GND | Ground (0V reference) |
| 14 | VCC | Positive Supply Voltage (4.75V to 5.25V) |
Truth Table
| Input A | Input B | Input C | Input D | Output Y |
|---|---|---|---|---|
| L | X | X | X | L |
| X | L | X | X | L |
| X | X | L | X | L |
| X | X | X | L | L |
| H | H | H | H | H |
Where: L = Low level (0V), H = High level (2.4V min), X = Don't care (either L or H)
Package Information
The 7421 is available in several package options:
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