📚 Standard Logic Gate Symbols | 标准逻辑门符号
In digital electronics, logic gates are the fundamental building blocks of circuits. They process binary inputs and produce a single binary output. Each gate type is represented by a unique standard symbol, making circuit diagrams easy to read and understand. The two common standards are the distinctive-shape symbols (often used in American and British textbooks) and the rectangular IEC symbols. This article will focus on the symbols specified in the IGCSE Cambridge Science syllabus, which typically uses the distinctive shapes.
在数字电子学中，逻辑门是电路的基本构建模块。它们处理二进制输入并产生单个二进制输出。每种门类型都由独特的标准符号表示，使电路图易于阅读和理解。两种常见标准是独特形状符号（常用于美国和英国教材）和矩形IEC符号。本文将重点介绍IGCSE剑桥科学大纲中规定的符号，通常使用独特形状。
1. Introduction to Logic Gates | 逻辑门简介
Logic gates operate on binary signals, where 1 represents a high voltage (usually true) and 0 represents a low voltage (false). There are seven basic gates: NOT, AND, OR, NAND, NOR, XOR, and XNOR. Memorising their symbols is essential for analysing and designing digital circuits.
逻辑门处理二进制信号，其中1代表高电压（通常为真），0代表低电压（假）。有七种基本门：非门、与门、或门、与非门、或非门、异或门和同或门。记住它们的符号对于分析和设计数字电路至关重要。
2. The NOT Gate Symbol | 非门符号
The NOT gate has one input and one output. Its symbol is a triangle pointing to the right, with a small circle (called an inversion bubble) at the output. The bubble indicates logical negation. If the input is A, the output is ¬A (often pronounced 'NOT A' or 'A bar').
非门有一个输入和一个输出。其符号是一个指向右侧的三角形，输出端有一个小圆圈（称为反相泡）。该圆圈表示逻辑否定。如果输入是A，输出是¬A（通常读作非A或A杠）。
In some diagrams the triangle is drawn as a buffer (without the bubble), but the presence of the bubble defines the NOT function. In the IGCSE exam, you must draw the triangle with the bubble clearly at the output.
在某些图中，三角形绘制为缓冲器（不带圆圈），但圆圈的添加定义了非功能。在IGCSE考试中，你必须绘制三角形，并在输出端清楚地画出圆圈。
Output = ¬A
3. The AND Gate Symbol | 与门符号
The AND gate has two or more inputs and one output. Its distinctive shape is a flat-ended D-shape with the curved side on the output. Inputs enter from the left, and the output exits on the right. The Boolean expression for two inputs A and B is A ⋅ B (A AND B). The output is 1 only when all inputs are 1.
与门有两个或更多输入和一个输出。其独特形状是一个平头的D形，弧形侧在输出端。输入从左侧进入，输出从右侧引出。对于两个输入A和B，布尔表达式为A ⋅ B（A与B）。仅当所有输入均为1时输出才为1。
Output = A ⋅ B
4. The OR Gate Symbol | 或门符号
The OR gate symbol is a curved shield-like shape that narrows to a point at the output. Inputs are drawn on the concave left side. For inputs A and B, the expression is A + B (A OR B). The output is 1 if at least one input is 1.
或门符号是一个弯曲的盾形，向输出端逐渐变尖。输入绘制在凹入的左侧。对于输入A和B，表达式为A + B（A或B）。如果至少有一个输入为1，输出即为1。
Output = A + B
5. The NAND Gate Symbol | 与非门符号
t;(A ⋅ B). It is one of the universal gates, meaning any other gate can be constructed using only NAND gates.
与非门是与门后接一个非门。其符号是与门形状，在输出端添加一个小圆圈（反相泡）。其功能是与门的补码：输出 = ¬(A ⋅ B)。它是通用门之一，意味着仅使用与非门即可构建任何其他门。
Output = ¬(A ⋅ B)
6. The NOR Gate Symbol | 或非门符号
The NOR gate combines an OR gate with a NOT operation. Its symbol is the OR shape plus an inversion bubble at the output. The Boolean expression is ¬(A + B). Like NAND, it is a universal gate. The output is 1 only when all inputs are 0.
或非门将或门与非操作组合。其符号是或门形状加上输出端的反相泡。布尔表达式为¬(A + B)。与与非门一样，它也是通用门。仅当所有输入均为0时输出才为1。
Output = ¬(A + B)
7. The XOR Gate Symbol | 异或门符号
The exclusive-OR (XOR) gate outputs 1 when an odd number of inputs are 1. For two inputs, it is 1 if A and B are different. Its distinctive symbol is like the OR gate but with an additional curved line on the input side (a double-curved line). The Boolean expression is A ⊕ B.
异或门（XOR）在输入中有奇数个1时输出1。对于两个输入，若A和B不同则输出1。其独特符号类似于或门，但在输入端增加了一条额外的弧线（双弧线）。布尔表达式为A ⊕ B。
ar symbol with =1 inside, but the curved-shape symbol is the one commonly tested in IGCSE.
注意：异或门符号没有反相泡。某些教材显示内部标有=1的矩形符号，但在IGCSE中常考的是曲线形状符号。
Output = A ⊕ B
8. The XNOR Gate Symbol | 同或门符号
The XNOR gate (exclusive-NOR) is the complement of XOR. It outputs 1 when the two inputs are equal. Its symbol is the XOR shape with an inversion bubble added at the output. The expression is ¬(A ⊕ B) or A ⊙ B. For two inputs, it acts as an equality detector.
同或门（XNOR）是异或门的补码。当
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