Digital-electronics 简明教程

Logic Gates in Digital Electronics

在数字电子学中， logic gate 是数字电路或数字系统的最基本组件。在本章中，我们将学习逻辑门的基本知识、其优点、局限性和应用。那么，让我们从“逻辑门”的基本定义开始吧。

In digital electronics, a logic gate is the most elementary component of a digital circuit or a digital system. In this chapter, we will learn the basics of logic gates, their advantages, limitations, and applications. So, let’s get started with the basic definition of a "logic gate".

What is a Logic Gate?

logic gate 是一种电子电路，它根据提供给它的输入执行逻辑运算，并产生一个可以为“真”或“假”的逻辑输出。

A logic gate is an electronic circuit that performs logical operations based on the inputs provided to it and produces a logical output that can be either "true" or "false".

逻辑门是所有数字电路和系统的主要构建模块。逻辑门的操作基于布尔数学。

Logic gates are the primary building blocks of all digital circuits and systems. The operation of logic gates is based on the Boolean mathematics.

Types of Logic Gates

逻辑门可以大致分为以下三类：

Logic gates can be broadly classified into the following three categories −

  1. Basic Logic Gates − AND Gate, OR Gate, NOT Gate

  2. Universal Logic Gates − NAND Gate and NOR Gate

  3. Derived Logic Gates − XOR Gate and XNOR Gate

所有这些门被组合在一起，以实现复杂的实用数字系统，以执行各种计算和逻辑运算。

All these gates are combined together to implement complex practical digital systems to perform various computational and logical operations.

Working Principle of Logic Gates

逻辑门的工作基于布尔代数定律。在布尔代数中，使用二进制变量和逻辑运算符执行运算。

The working of logic gates is based on the laws of Boolean algebra. In Boolean algebra, the binary variables and logical operators are used to perform operations.

布尔变量可以有两个可能的值，即 0 或 1。其中，0 表示“假”或“低态”，而 1 表示“真”或“高态”。

A Boolean variable can have one of the two possible values, i.e., 0 or 1. Where, 0 represents "false" or "low state" while 1 represents "true" or "high state".

每个逻辑门的操作使用输入变量和输出变量的表进行描述，该表称为逻辑门的 truth table 。

The operation of each logic gate is described using a table of input and output variables, which is called truth table of the logic gate.

逻辑门根据其真值表中描述的关系生成一个特定输出。因此，布尔代数构成了逻辑门工作的基础。

A logic gate produces a specific output depending on the relationship described in its truth table. Hence, Boolean algebra forms the foundation of working of logic gates.

Major Components of Logic Gates

逻辑门由多个电子元件组成，其中一些在此处列出 −

A logic gate consists of several electronic components, some of which are listed here −

Transistor

晶体管是用于设计逻辑门电路的主要电子元件。将许多晶体管连接在一起以形成一个电路，该电路可以执行不同的逻辑门函数。

Transistors are the main electronic components used to design a logic gate circuit. A number of transistors are connected together to form a circuit that can perform different logic gate functions.

Input Terminals

逻辑门可以有一个或多个输入端。每个输入端可以接收二进制信号。

A logic gate can have one or more input terminals. Each input terminal can receive binary signals.

Output Terminals

逻辑门具有输出端，该输出端产生逻辑门执行的逻辑运算的结果。

Logic gates have an output terminal that produces the result of the logical operation performed by the logic gate.

Power Supply

作为电子电路，逻辑门需要电能才能工作。通常，电压 VCC 代表电源。

Being an electronic circuit, a logic gate requires a source of electric power to work. In general, a voltage VCC represents the power supply.

Ground Terminal

地端是一个 0 V 端。它充当逻辑门电路中的参考点。

The ground terminal is a 0 V terminal. It acts as a reference point in the circuitry of the logic gate.

Connecting Wires

这些是逻辑门电路中的基本元件。连接线用于在电路中连接晶体管和逻辑门的其他元件。

These are essential components in the logic gate circuitry. The connecting wires are required to connect transistors and other components of a logic gate in a circuit.

这些是逻辑门的必要组成部分，对于设计和实现逻辑门至关重要。然而，一些先进的逻辑门也可以有更多的电路元件。

These are the main components of a logic gate essentially required to design and implement it. However, some advanced logic gates can have some more circuit components as well.

Advantages of Logic Gates

逻辑门在数字电子领域发挥着重要作用。逻辑门有许多优点，因此它们广泛应用于各种应用中。

Logic gates play an important role in the field of digital electronics. Logic gates have numerous advantages due to which they are widely used in various applications.

逻辑门的一些主要优点如下 −

Some of the major advantages of logic gates are given below −

  1. Logic gates can process digital signals which are essential component in modern computing systems.

  2. Logic gates can perform logical or Boolean operations efficiently.

  3. Being digital circuits, logic gates are highly immune to noise and electromagnetic interference. Hence, they are more reliable.

  4. Multiple logic gates can be combined to obtain higher order logic gates and design complex digital systems.

  5. Logic gates are versatile in terms of logical operations, as they can perform a variety of operations when configured in different ways.

  6. Logic gates have high operating speed.

  7. Logic gates consume lower amount of electric power. Hence, they result in higher energy efficiency.

  8. Logic gates can be integrated in the form ICs. This feature enables engineers to design compact and efficient electronic devices.

所有这些优点使逻辑门成为数字电子领域中的基本组件。

All these advantages make logic gates the essential components in the field of digital electronics.

Limitations of Logic Gates

逻辑门具有诸多优势，但也有一些局限性和缺点。

Logic gates have several advantages, but they also have some limitations and drawbacks.

逻辑门的主要局限性如下所述——

The main limitations of logic gates are described below −

  1. Logic gates have a finite propagation delay and take a certain amount of time to process. This can be a limiting factor in case of high-speed digital systems.

  2. In some complex digital systems, logic gates can degrade the quality of the signals.

  3. Logic gates can operate with binary voltage levels only.

  4. In large digital circuits, the use of multiple logic gates can increase complexity of the circuit.

  5. The continuous switching i.e., toggle between on and off states can heat up the logic gates and degrade their performance.

  6. Design, fabrication, and testing of logic gate is a complex and cost intensive process.

  7. Logic gates require addition analog to digital converts to process analog signals.

  8. Logic gates are highly sensitive faults and errors.

Applications of Logic Gates

正如我们已经讨论过的，逻辑门是所有数字电路和系统的基本构建模块。因此，它们在数字电子中广泛用于各种应用。以下是逻辑门的一些主要应用——

As we already discussed that logic gates are the primary building blocks of all digital circuits and systems. Hence, they are used in a wide range of applications in digital electronics. The following are some key applications of the logic gates −

  1. Logic gates are used in digital computers to perform arithmetic, logical, and control functions.

  2. In memory devices, logic gates are used to implement memory cells to store digital data in the form of bits.

  3. Logic gates are used in manufacturing microprocessors and microcontrollers.

  4. In systems used in the digital signal processing, the logic gates play an important role to perform various operations such as modulation, filtering, algorithm execution, etc.

  5. Logic gates are also used in digital communication systems to perform functions like encoding, decoding, signal processing, etc.

  6. In control systems, logic gates are used to manage and control the operations of machinery.

  7. Logic gates are also used to implement automated operation of security systems.

Conclusion

总之，逻辑门是一种基于布尔代数原理工作的电子电路，执行各种逻辑运算。

In conclusion, a logic gate is an electronic circuit that works on the principle of Boolean algebra and performs various logical operations.

逻辑门是数字电子系统中的基本构建模块。它们广泛用于数字系统中，执行诸如控制、处理、操作数字数据等操作。

Logic gates are the fundamental building blocks of digital electronic systems. They are widely used in digital systems to perform operations such as controlling, processing, manipulation of digital data, etc.

在本章中，我们解释了逻辑门的概念基础及其应用。在接下来的章节中，我们将详细讨论不同类型的逻辑门，如或门（OR）、与门（AND）、非门（NOT）、与非门（NOR）、或非门（NAND）等。

In this chapter, we explained the basic concepts of logic gates and their applications. In the next chapters, we will discuss about different types of logic gates such as OR, AND, NOT, NOR, NAND, etc. in detail.