# logic gate



## mido_bigshow (4 سبتمبر 2007)

*Logic Gate*







[SIZE=-1]AND | OR | XOR | NOT | NAND | NOR | XNOR[/SIZE]
A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. At any given moment, every terminal is in one of the two binary conditions _low_ (0) or _high_ (1), represented by different voltage levels. The logic state of a terminal can, and generally does, change often, as the circuit processes data. In most logic gates, the low state is approximately zero volts (0 V), while the high state is approximately five volts positive (+5 V).
There are seven basic logic gates: AND, OR, XOR, NOT, NAND, NOR, and XNOR.​The _AND gate_ is so named because, if 0 is called "false" and 1 is called "true," the gate acts in the same way as the logical "and" operator. The following illustration and table show the circuit symbol and logic combinations for an AND gate. (In the symbol, the input terminals are at left and the output terminal is at right.) The output is "true" when both inputs are "true." Otherwise, the output is "false." 





*AND gate*​*Input 1**Input 2**Output*000010100
111​The _OR gate_ gets its name from the fact that it behaves after the fashion of the logical inclusive "or." The output is "true" if either or both of the inputs are "true." If both inputs are "false," then the output is "false." 




*OR gate*​*Input 1**Input 2**Output*000011101111
​The _XOR_ (_exclusive-OR_) _gate_ acts in the same way as the logical "either/or." The output is "true" if either, but not both, of the inputs are "true." The output is "false" if both inputs are "false" or if both inputs are "true." Another way of looking at this circuit is to observe that the output is 1 if the inputs are different, but 0 if the inputs are the same. 




*XOR gate*​*Input 1**Input 2**Output*000011101110​A logical _inverter_, sometimes called a _NOT gate_ to differentiate it from other types of electronic inverter devices, has only one input. It reverses the logic state. 




*Inverter or NOT gate*​*Input**Output*10
01​The _NAND gate_ operates as an AND gate followed by a NOT gate. It acts in the manner of the logical operation "and" followed by negation. The output is "false" if both inputs are "true." Otherwise, the output is "true." 




*NAND gate*​*Input 1**Input 2**Output*001011101110​The _NOR gate_ is a combination OR gate followed by an inverter. Its output is "true" if both inputs are "false." Otherwise, the output is "false." 




*NOR gate*​*Input 1**Input 2**Output*001010100110​The _XNOR (exclusive-NOR) gate_ is a combination XOR gate followedby an inverter. Its output is "true" if the inputs are the same, and"false" if the inputs are different. 




*XNOR gate*
*Input 1**Input 2**Output*001010100111​Using combinations of logic gates, complex operations can be performed. In theory, there is no limit to the number of gates that can be arrayed together in a single device. But in practice, there is a limit to the number of gates that can be packed into a given physical space. Arrays of logic gates are found in digital integrated circuits (ICs). As IC technology advances, the required physical volume for each individual logic gate decreases and digital devices of the same or smaller size become capable of performing ever-more-complicated operations at ever-increasing speeds.​
منقول​


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## م.محمد الكسواني (5 سبتمبر 2007)

Thank you very much...


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## geniusse01 (21 سبتمبر 2007)

مشكووووووور على الموضوع يا باشا.


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## محمد آل عيسى (21 سبتمبر 2007)

شكرا جزيلا


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## e_faisal83 (16 أكتوبر 2007)

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## عمان16 (16 أكتوبر 2007)

موضوع رائع...


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## kalcol (16 أكتوبر 2007)

مشكورر على الجهد المبذول 
وجاء هذا الدرس في وقته

مشكوووووووووور


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## SKR (18 أكتوبر 2007)

مشكوووووووووور مجهود رائع


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