Digital-electronics 简明教程

NOT Gate in Digital Electronics

NOT gate 是仅有一个输入线和一个输出线的基本逻辑门类型。它执行反转操作。

The NOT gate is a type of basic logic gate having only one input line and one output line. It performs the inversion operation.

在本章中，我们将解释 NOT 门的理论、逻辑符号、工作原理、真值表、布尔表达式等。

In this chapter, we will explain the theory of NOT gate, its logic symbol, working, truth table, Boolean expression, etc.

在数字电子学中，NOT 门用作复杂数字系统的基本构建块。

In digital electronics, the NOT gate is used as the basic building block of complex digital systems.

What is a NOT Gate?

NOT gate 是用于在数字电子学中实现反转函数的基本逻辑门类型。由于它执行反转运算，因此也称为 inverter 。

The NOT gate is a type of basic logic gate used in digital electronics to implement the inversion function. Since it performs the inversion operation, it is also known as inverter.

它仅有一个输入线和一个输出线。当 NOT 门的输入为低电平或逻辑 0 时，其输出为高电平或逻辑 1。当 NOT 门的输入为高电平或逻辑 1 时，其输出为低电平或逻辑 0。

It has only one input line and one output line. The output of the NOT gate is high or logic 1 when its input is low or logic 0. The output of the NOT gate is low or logic 0 when its input is high or logic 1.

NOT 门的逻辑符号如下图所示 −

The logic symbol of the NOT gate is shown in the following figure −

在此， A 是输入行， Y 是 NOT 门的输出行。

Here, A is the input line and Y is the output line of the NOT gate.

Truth Table of NOT Gate

NOT 门的真值表是输入和输出的表格，它表示了它们之间的关系。以下是 NOT 门的真值表 −

The truth table of NOT gate is a table of input and output that represent the relationship between them. Here is the truth table of the NOT gate −

Input (A)

Output (Y)

从真值表中，我们可以观察到 NOT 门会反转对它应用的输入。因此，如果我们应用高电平输入，它会产生低电平输出，反之亦然。

From this truth table, we can observe that the NOT gate inverts the input applied to it. Hence, if we apply a high input, it produces a low output and vice-versa.

Boolean Expression of NOT Gate

NOT 门的布尔表达式是一个逻辑函数，它在数学上解释了 NOT 门的输入和输出之间的关系。

The Boolean expression of the NOT gate is a logical function that explains the relationship between input and output of the NOT gate mathematically.

NOT 门的布尔表达式给出如下 −

The Boolean expression of the NOT gate is given below −

\mathrm{Y \: = \: \bar{A} \: = \: A'}

在此，符号“(-) 上划线”和“(') 上标”表示反转或补运算。

Here, the symbols "(-) overbar" and "(') prime" represents the inversion or complement operation.

这个表达式以“Y 等于 A 上划线或 A 上标或非 A”来读。

This expression is read as "Y is equal to A bar or A prime or NOTed A".

Working of NOT Gate

NOT 门对应用的输入执行反转运算。NOT 门对可能的输入组合的完整工作原理解释如下 −

The NOT gate performs the inversion operation of the input applied. The complete working of the NOT gate for possible input combinations is explained below −

If A = 0, the output is Y = 1.
If A = 1, the output is Y = 0.

因此，NOT 门的输出是对应用到它上面的输入的补码。

Thus, the output of the NOT gate is the complement of the input applied to it.

NOT Gate using Transistor

我们可以使用 BJT 晶体管来实现 NOT 门逻辑。用晶体管实现 NOT 门时，称为 transistor inverter 。

We can implement the NOT gate logic by using a BJT transistor. When the NOT gate is implemented using a transistor, it is called a transistor inverter.

下图显示了使用晶体管或晶体管反相器的 NOT 门电路图。

The following figure shows the circuit diagram of a NOT gate using transistor or transistor inverter.

Working of Transistor NOT Gate

上述晶体管反相器电路的工作原理如下 −

The above transistor inverter circuit operates as described below −

When the input A is low ，晶体管将处于非激活状态并作为开路开关。因此，电源 VCC 和接地端之间没有闭合路径。因此，总电源电压将出现在输出行上。这表示高或逻辑 1 输出。

When the input A is low, the transistor will be inactive and acts as an open switch. Thus, there is no closed path between the power supply VCC and ground terminal. Hence, the total supply voltage will appear at the output line. This represents the high or logic 1 output.

When the input A is high ，晶体管将导通并作为闭合开关。因此，电源直接连接到接地端，而且在输出行上可用的电压等于接地电压。这使得电路的输出变低或变为逻辑 0。

When the input A is high, the transistor will turn on and act as a closed switch. As a result, the power supply is directly connected to the ground terminal and the voltage available at the output line is equal to the ground voltage. This makes the output of the circuit low or logic 0.

这就是上述晶体管电路如何实现 NOT 逻辑。

This is how, the above transistor circuit implements the NOT logic.

NOT Gate using Switches

我们还可使用电池、开关和灯来实现 NOT 门运算。使用开关的 NOT 门的电路图显示在下图中。

We can also implement the NOT gate operation using a battery, a switch, and a lamp. The circuit diagram for the NOT gate using switches is shown in the following figure.

在该电路中，当开关 A 是打开的，即逻辑 0，电流沿路径流过灯泡使其发光。这表示一个高电平或逻辑 1 输出。

In this circuit, when the switch A is open, i.e., logic 0, the current follows the path through the lamp making it glow. This represents a high or logic 1 output.

如果开关 A 是闭合的，即逻辑 1，电流会沿闭合开关提供的短路路径流动，不会有电流流过灯泡。因此，在这种情况下，灯泡会关闭并表示低电平或逻辑 0 输出。

If the switch A is closed, i.e., logic 1, the current flows through the short-circuited path provided by the closed switch and no current will flow through the lamp. Hence, in this case, the lamp will be off and represents the low or logic 0 output.

从该讨论可以清楚看出，当输入为低电平时，输出为高电平；反之亦然。因此，上述开关电路实现了非门逻辑。

From this discussion, it is clear that the output is high when the input is low and vice-versa. Thus, the above switching circuit implements the NOT gate logic.

NOT Gate IC

非门以集成电路或 IC 的形式出现。最常用的非门 IC 是 IC 7404。它包含六个 TL（晶体管逻辑）非门。

The NOT gate comes in the form of integrated circuits or ICs. The most commonly used NOT gate IC is IC 7404. It contains six TL (transistor logic) NOT gates.

非门 IC 7404 的引脚图如在下图所示。

The pin diagram of the NOT gate IC 7404 is depicted in the following figure.

Applications of NOT Gate

非门是各种数字系统和电路的基本构建模块。下面描述了非门的一些主要应用：

The NOT gate is an essential building block of various digital systems and circuits. Some key applications of NOT gate are described below −

NOT gate is used in inverters to convert a high signal to a low signal and a low signal to a high signal.
NOT gate is used in communication systems and storage devices.
NOT gate is also employed as interfacing device between different logic families.
NOT gate is also used in various digital circuits like timers, oscillators, multivibrators, modulators, etc.

Conclusion

总之，非门是数字电子设备中用于实现反相操作的逻辑门。它只有一个输入线和一个输出线。

In conclusion, the NOT gate is a logic gate used in digital electronics to implement inversion operation. It has only one input line and one output line.

非门输出是施加在其上的输入信号的补码。在本章中，我们解释了非门的基本理论，以及其工作原理和应用。

The output of the NOT gate is the complement of the input signal applied to it. In this chapter, we explained the basic theory of NOT gate along with its working and applications.