why nand and nor are universal gates

The Universal Capability of NAND and NOR Gates NAND and NOR gates are universal logic gates. The AND, Or, Nor and Inverter functions can all be performed using only NAND gates. The AND, OR, NAND and Inverter functions can all be performed using only NOR gates. An inverter can be made from a NAND or a NOR by connecting all inputs of the gate together. If the output of a NAND gate is inverted, it becomes an AND function. If the output of a NOR gate is inverted, it becomes an OR function. If the inputs to a NAND gate are inverted, the gate becomes an OR function. If the inputs to a NOR gate are inverted, the gate becomes an AND function. When NAND gates are used to make the OR function and the output is inverted, the function becomes NOR. When NOR gates are used to jake the AND function and the output is inverted, the function becomes NAND.
A logic gate is an elementary building block of a. Most logic gates have two inputs and one output.


At any given moment, every terminal is in one of the two conditions low (0) or high (1), represented by different 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 (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 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 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 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 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 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 The XNOR (exclusive-NOR) gate is a combination XOR gate followed by an inverter. Its output is true if the inputs are the same, and false if the inputs are different. XNOR gate 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 ( ). 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. Continue Reading About logic gate (AND, OR, XOR, NOT, NAND, NOR and XNOR)

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