SN74LS21D

Product Overview

• Category: Integrated Circuit (IC)
• Use: Logic Gates
• Characteristics: Dual 4-input Positive-AND Gate
• Package: DIP-14 (Dual In-line Package with 14 pins)
• Essence: Combines four input signals and provides a single output signal based on the AND logic operation.
• Packaging/Quantity: Available in reels or tubes, typically sold in quantities of 25 or more.

Specifications

• Supply Voltage Range: 4.75V to 5.25V
• Input Voltage Range: 0V to VCC
• Output Voltage Range: 0V to VCC
• Operating Temperature Range: -40°C to +85°C
• Propagation Delay Time: 9 ns (typical)
• Power Dissipation: 22 mW (typical)

Detailed Pin Configuration

The SN74LS21D has a total of 14 pins, which are assigned as follows:

1. A1: Input A1
2. B1: Input B1
3. C1: Input C1
4. D1: Input D1
5. Y1: Output Y1
6. GND: Ground
7. Y2: Output Y2
8. D2: Input D2
9. C2: Input C2
10. B2: Input B2
11. A2: Input A2
12. VCC: Supply Voltage
13. NC: No Connection
14. NC: No Connection

Functional Features

The SN74LS21D is a dual 4-input positive-AND gate that performs logical AND operations on four input signals. It combines the inputs using internal circuitry and produces a single output signal. The device operates on a supply voltage range of 4.75V to 5.25V and is compatible with TTL (Transistor-Transistor Logic) levels.

Advantages and Disadvantages

Advantages: - Dual 4-input configuration allows for versatile logic operations. - Wide supply voltage range ensures compatibility with various systems. - Fast propagation delay time enables high-speed operation.

Disadvantages: - Limited number of inputs may restrict complex logic operations. - Requires external pull-up resistors for proper operation in some applications.

Working Principles

The SN74LS21D consists of internal circuitry that combines the four input signals using AND gates. The logical AND operation is performed on each corresponding pair of inputs, and the results are combined to produce the output signal. The device operates based on the principles of digital logic, where logical high and low states represent binary values of 1 and 0, respectively.

Detailed Application Field Plans

The SN74LS21D can be used in various applications that require logical AND operations. Some common application fields include:

1. Digital Electronics: Used in combinational logic circuits to perform logical AND operations on multiple input signals.
2. Microcontrollers: Employed as a part of input/output (I/O) interfaces to process multiple input signals.
3. Data Processing: Integrated into data processing systems to perform bitwise logical operations on data streams.
4. Control Systems: Utilized in control systems to implement decision-making logic based on multiple input conditions.

Detailed and Complete Alternative Models

1. SN74LS08: Quad 2-input Positive-AND Gate
2. SN74LS11: Triple 3-input Positive-AND Gate
3. SN74LS20: Dual 4-input Positive-NAND Gate
4. SN74LS32: Quad 2-input Positive-OR Gate

These alternative models offer similar functionality to the SN74LS21D and can be used as replacements depending on specific requirements.

In conclusion, the SN74LS21D is a dual 4-input positive-AND gate integrated circuit. It combines four input signals using AND logic to produce a single output signal. The device operates on a wide supply voltage range and has a fast propagation delay time. It finds applications in digital electronics, microcontrollers, data processing, and control systems. Alternative models such as the SN74LS08, SN74LS11, SN74LS20, and SN74LS32 offer similar functionality.