7420
7420 Dual 4-Input NAND Gate - Technical Summary
Overview
The 7420 is a dual 4-input NAND gate integrated circuit belonging to the 7400 series of transistor-transistor logic (TTL) devices. This component provides two independent NAND gates, each accepting four input signals and producing a single output based on the logical NAND operation. The 7420 is widely used in digital logic design for its reliability, speed, and compatibility with other TTL family components.
As a fundamental building block in digital electronics, the 7420 implements the Boolean logic function Y = NOT (A AND B AND C AND D) for each of its two gates. The output goes low only when all four inputs are high, adhering to standard NAND gate truth table behavior.
Features
- Dual 4-input NAND gates in a single package
- Standard TTL switching voltages (0.8V max for LOW, 2.0V min for HIGH)
- Typical propagation delay of 10-15 ns
- Fan-out of 10 standard TTL loads
- Wide operating temperature range (0°C to +70°C commercial grade)
- 14-pin DIP (Dual In-line Package) configuration
- Compatible with most TTL and DTL logic families
- Low power consumption (typical 10mW per gate)
- High noise immunity characteristic of TTL devices
Applications
The 7420 finds extensive use in various digital logic applications including:
- General purpose logic circuits
- Address decoding systems
- Data routing and multiplexing
- Arithmetic logic units (ALUs)
- Clock generation and conditioning circuits
- Error detection and correction systems
- Control logic implementation
- Input conditioning for microprocessor systems
- Glitch suppression circuits
- Pulse shaping networks
Electrical Characteristics
Absolute Maximum Ratings
- Supply Voltage (Vcc): 7V
- Input Voltage: 5.5V
- Operating Temperature Range: 0°C to +70°C
- Storage Temperature Range: -65°C to +150°C
Recommended Operating Conditions
- Supply Voltage (Vcc): 4.75V to 5.25V
- High-Level Input Voltage (VIH): 2.0V min
- Low-Level Input Voltage (VIL): 0.8V max
- Output Current High (IOH): -400μA
- Output Current Low (IOL): 16mA
DC Characteristics (Vcc = 5V, TA = 25°C)
- High-Level Output Voltage (VOH): 2.4V min, 3.4V typical
- Low-Level Output Voltage (VOL): 0.2V typical, 0.4V max
- Input Clamp Voltage (VIK): -1.5V max at IIK = -18mA
- High-Level Input Current (IIH): 40μA max
- Low-Level Input Current (IIL): -1.6mA max
- Short-Circuit Output Current (IOS): -18mA to -55mA
- Supply Current (ICC): 8mA typical, 16mA max
AC Characteristics
- Propagation Delay Time (tPLH, tPHL): 15ns max at CL = 15pF, RL = 400Ω
- Transition Time (tTLH, tTHL): 15ns max
- Power Dissipation Capacitance (CPD): 20pF typical
Package Information
14-Pin DIP (Dual In-line Package)
The 7420 is typically available in a standard 14-pin plastic dual in-line package (PDIP) with the following pin configuration:
- Pin 1: 1A (Input A for Gate 1)
- Pin 2: 1B (Input B for Gate 1)
- Pin 3: N.C. (No Connection)
- Pin 4: 1C (Input C for Gate 1)
- Pin 5: 1D (Input D for Gate 1)
- Pin 6: 1Y (Output for Gate 1)
- Pin 7: GND (Ground)
- Pin 8: 2Y (Output for Gate 2)
- Pin 9: 2A (Input A for Gate 2)
- Pin 10: 2B (Input B for Gate 2)
- Pin 11: N.C. (No Connection)
- Pin 12: 2C (Input C for Gate 2)
- Pin 13: 2D (Input D for Gate 2)
- Pin 14: VCC (Positive Supply Voltage)
Physical Dimensions
- Package Type: PDIP-14
- Length: 19.3mm (0.76 inches)
- Width: 6.35mm (0.25 inches)
- Height: 4.57mm (0.18 inches)
- Lead Pitch: 2.54mm (0.1 inches)
- Lead Length: 3.3mm (0.13 inches)
Truth Table
The following truth table describes the logical operation of each NAND gate within the 7420:
| Input A | Input B | Input C | Input D | Output Y |
|---|---|---|---|---|
| L | X | X | X | H |
| X | L | X | X | H |
| X | X | L | X | H |
| X | X | X | L | H |
| H | H | H | H | L |
Where: L = Low logic level (≤0.8V), H = High logic level (≥2.0V), X = Don't care (either L or H)
Design Considerations
When implementing the 7420 in circuit designs, several important factors should be considered:
