From the truth table, we can say that the output of the or logic or an or gate is true or high or 1, even if either or both of a or b are 1. The old techinterview forum xor gate using nand gates. And gate, and a nand gate with complemented inputs acts as an or gate. The nand gate represents the complement of the and operation. It produces a 1 output when any of the inputs is 0. I just cant seem to figure out how to replace the or gate with anything other than 3 nand gates, which doesnt leave enough to replace the and gates. The other important ic gate type is the sum modulo two, or exclusiveor xor gate, which has a high output only when an odd number of its inputs are high. Perform the following steps to obtain the minimum number of gates required. The schematic of xor gate using cmos logic is shown in figure 4. Therefore, we can use a nand gate to implement all three of the elementary operators and,or,not. The gate has good performance even when we redesigned it in the.
Xor gate sometimes eor, or exor and pronounced as exclusive or is a digital logic gate that gives a true 1 or high output when the number of true inputs is odd. One nand input pin is connected to the input signal a while all other input pins are connected to logic 1. Schematic of xor using cmos logic by using transmission gates logic, the number of transistors is reduced from the conventional cmos xor gate. How to make a 3 input xor gate with nand gates quora. Alloptical multiple logic gates with xor, nor, or, and nand functions using parallel soamzi structures. And thus, it can be aptly termed as universal gate. At any given moment, every terminal is in one of the two binary conditions false high or true low. Note here that the truth table of the xnor gate is the complement of the xor gate. For example, the function notx may be equivalently expressed as nand x,x. Xor gate is a basic logic gate in digital system that use the combination of and and or gates. Figure 5 there is another configuration that implies the same output of previous circuit figure 6 r1 vcc vb vcc 0 r1 va. Used to build logic functions there are seven basic logic gates.
Taken to limit, give me as many nand gate as i want, in theory i can build a pentium processor. Logic gates not, or, and, nor, nand, xor, xnor gate, pdf. Basic logic gates using nand gate not, or, and gates. Hence the nand gate is made up of and gate which is followed by an inverter. Xor gate of the proposed scheme is derived from the. The three gates or, and and not, when connected in various combinations, give us basic logic gates such as nand, nor gates, which are the universal building blocks of digital circuits. A novel design for xor gate used for quantumdot cellular. So, from the above discussion, it is clear that all the three basic gates and, or, not can be made by only using nor gate. Npn transistor xor gate circuit sully station technologies.
Pdf realization of alloptical xor, nor, and nand gates in. The performance of soamzibased xor gate have been analyzed through numerical simulations, to generalize the optimal parameters as well as the suitable operating conditions 914. Jul 08, 2015 the equivalent circuit of nand gate using diodes and transistors is shown below. A logic gate is a building block of a digital circuit.
The two input nand gate can be extended to three inputs by placing three nfets in series and three pfets in parallel as in figure 3. The output of a xor gate is obtained true only if one of its inputs is true. Exclusiveor gate tutorial the exclusiveor logic function is a very useful circuit that can be used in many different types of computational circuits in the previous tutorials, we saw that by using the three principal gates, the and gate, the or gate and the not gate, we can build many other types of logic gate functions, such as a nand gate. The circuits of half adder and full adder using xor gate are shown in the following image. This basic logic gate is the combination of and and not gate. Ppt basic logic gates powerpoint presentation free to. Realization of alloptical xor, nor, and nand gates in single format by using semiconductor optical amplifiers article pdf available in japanese journal of applied physics 461. Exhaustive search shows its not possible to use fewer nand gates than this. Jan 28, 2017 realization of xor gate using minimum number of two inputs nand gate. Lets take a look at the symbol and truth table for or gate first. The basic logic gates arethe inverter or not gate, the and. This table shows that the output of an xor gate with input x 1 and x 2 is given by x 1. Simplification of boolean functions using the theorems of boolean algebra, the algebraic.
For example, the, apollo guidance computer, was built exclusively from nor gates, about 5,600 in total for the later versions. Each output and output of a logic gate is represented by binary conditions 0 low and 1 high. Basic gates 1 and gate 2 or gate 3 not gate universal gates 1 nand gate 2 nor gate derived gates 1 xor gate 2 xnor gate and function text description output y is true if inputs a and b are true, else it is false. Exclusiveor gate tutorial with exor gate truth table. Basic logic gates types, functions, truth table, boolean. What is logic gate and, or, xor, not, nand, nor and xnor. Logic gates digital circuit that either allows a signal to pass through it or not.
This means, any boolean expression can be reexpressed by an equivalent expression utilizing only nand operations. Im working on a project in verilog that will encrypt a 20bit number and decrypt it back using xor, not, and nand gates. Twolevel digital circuit implementations using other gates. Logic gates a b out 0 0 0 0 1 1 1 0 1 1 1 1 a b out 0 0 0 0 1 0 1 0 0. Experiment 2 basic logic gates implementation using breadboards. Boolean logical algebra prove 4 nor gates to an xnor gate. The number of transistors required to implement an ninput logic gate is 2n. For encryption, input xor xorencdec predefined operand for xor not input also 1s comp input nand nandencdec predefined operand for nand i have a problem with my decryptor. The circuit diagram is similar to that of not gate made by using only nand gate. This construction entails a propagation delay three times that of a single nand gate and uses five gates.
The example transistor xor gate circuit is implemented here using pn2222a npn transistors a variant of the 2n2222a but many common npn bipolar junction transistors. Apologies for the quality of images using nand gate. Logic gates truth table logic gates applications universal logic gates. Introduction to logic gates projectiot123 technology. All the anded literals can be realized directly using a nand gate each. To derive the rules of boolean algebra related to an xor gate, i take the basic point of standard rules and substitutes the standard rules with an xor gate function. The inputs to the nand gate is applied through the diodes and these diodes are connected to bjt. Nor, and nand gates in single format by using semiconductor optical amplifiers. If both inputs are false 0low or both are true, a false output results.
An exclusive or gate or xor gate is a digital logic gate composed of more inputs and only one output as shown in fig. A cd4011b was used as an example of a nand gate ic. Drive xor from nand gate, nand to xor conversion with. Realization of alloptical xor, nor, and nand gates in single format. Help explain this boolean equation xor with nor gates. I mean intuitively, to me, i should get this one if i do it step by step followed by the definition xor a and not b or not a and b. Logic nand gates are available using digital circuits to produce the desired logical function and is given a symbol whose shape is that of a standard and gate with a circle, sometimes called an inversion bubble at its output to represent the not gate symbol with the logical operation of the nand gate given as. The exor gate is defined as, the hybrid logic gate with 2 or more inputs to perform the exclusive disjunction operation. The nand boolean function has the property of functional completeness. I am not very good at ascii art so i couldnt provide gates and bubbles. Very quickly, below are the symbols, boolean expression and truth table of nand and nor gates. Pdf alloptical multiple logic gates with xor, nor, or. Understand how to implement simple circuits based on a schematic diagram using logic gates. Exclusiveor xor digital logic gate electrical technology.
Several kinds of digital logic circuits are the basic elements that form the building blocks for such complex digital system as the. If both the inputs are same, then the output is low. Jan 30, 2017 we discussed about how to make xor and xnor gate using nand gate. The diagram above table of truth for the adder suggests that all we need is a xor and and gates. There are many uses for an xor gate, but the prototypical usage is as part of an adder, as a halfadder, which adds two binary digits. Logic gates and truth table and, or, not, nor, nand, xor. Universal gates in digital electonics nand and nor. Digital logic basics 21 implementation using nand gates. The problem is to design a system with the same truth table, but made from. The figure shows two ways in which a nor gate can be used as an inverter not gate. In digital electronics, a nand gate notand is a logic gate which produces an output which is false only if all its inputs are true. And gate, or gate and not gate, nor gates, nand gates, xor gates, xnor gates etc. Neural representation of and, or, not, xor and xnor logic. Watch this video to learn more and see the interesting practical.
Lab6 designing nand, nor, and xor gates for use to design. Depending on the type of logic gate being used and the. Discrete xor gate can be made with mosfets and diodes. What is the function of the xor gate in a digital circuit. The working of these gate is like that we get binary 1 at the output of the gate if and only is both the input is at the binary low state i. Xor from nand logic, nand to xor conversion, equations, circuit, minimizatio truth tables. Lab6 designing nand, nor, and xor gates for use to. A nand gate is made using transistors and junction diodes. Logic gate actually the term logic is applied to digital circuits used to implement logic functions. Xor gate in combination to other basic can be wired to form half adder and full adder circuit. It produces a 0 output only when all the inputs are 1. An or gate equivalent can also be constructed using only nand gates, by putting two shorted equivalent to not nand gates each at the input of a third nand gate as shown in figure 4. Digital circuitsnor logic wikibooks, open books for an. All nor input pins connect to the input signal a gives an output a.
Since we have available only nand and nor gates, a bit a boolean algebra comes timely to the rescue. And, or, not, nand not and, nor not or, xor, and xnor not xor later building functions. The above diagram is of a not gate made by using a nor gate. Now let us see how each logic gate can be created with nand and nor gates. Now to make a nor gate, using 4 mosfets just like the nand gate. Design of ultra compact alloptical xor, xnor, nand and or. Logic gates and, or, not, nor, nand, xor, xnor gates. So if and, or and not gates can be implemented using nand gates only, then we prove our point.
Logic nand gate tutorial with nand gate truth table. Continuing the process, the nand gate can be further extended to more three inputs as well. Using ltspice and irsim, here are the simulations of the logical operation of the gate for all 4 possible input. Wire and operate logic gates such as and, or, not, nand, nor, xor. Redraw the circuit, replacing each gate with its nand. Xor gate can be realized with four two inputs nand gates.
Not, or, and and gates are the basic types of gates. To make it easy, just copy and change the schematic file used for the nand gate, to avoid tediuos work. These two hybrid logic gates are called the exclusiveor exor gate and its complement the exclusivenor exnor gate. Pdf realization of alloptical xor, nor, and nand gates. May 24, 2014 logic gates and, or, not, nor, nand, xor, xnor gates. I am trying to design a full adder just 1 bit using only 4 xor gates and 4 nand gates in other words, the 7486 and 7400 ics. Sep 07, 2015 the nand gate is just a combination of the expression not gate as well as and gate. Like nand gates, nor gates are socalled universal gates that can be combined to form any other kind of logic gate. This video takes the viewers, step by step to four different derived gates, i.
All nand input pins connect to the input signal a gives an output a. Therefore, any switching function can be constructed using only nand gates. Today, contrary to popular belief, integrated circuits are not constructed exclusively from a single type of gate. The xor circuit with 2 inputs is designed by using and, or and not gates is shown above. Nand gate, we can build the three basic logic operators. From this logical expression, we can derive the following nand gate implementation. However, when i try to do so step by step by replacing all gates using nand and cancelling two nand gates that are in cascade, i always end up getting 5 nand gates instead of 4. Logic gates project 7 segment display circuit using logic gates. The outputs of all anded literals are then fed into one nand gate to realize sop sum of product expression as a whole.
As a result, we can build any logic circuit and implement any boolean expression. I mean intuitively, to me, i should get this one if i do it step by step followed by the definition xor. A nand gate presents an and gate followed by an inverter. Add not gate to the output of xor gate as shown in the image above. Pdf alloptical multiple logic gates with xor, nor, or, and. The operation is the same as for the two input nand gate, satisfying all three basic rules. Logic gates ppt boolean algebra electronic engineering. The output of 2 input xor gate is high only when one of its inputs are high. In the field of digital electronic circuits, this implies that we can implement any boolean function using just nand gates. Nand and nor gates are called universal gate because you can construct any gate using nand gate or nor gate. Design of a xor gate out of nand and nor gates tasks first, verify explicitly making a corresponding table of truth the following properties.
The table of combinations for a twoinput xor gate is given in table 6. Although xor gate can be used in a variety of applications two most common and simplest applications of xor gate is its use in half adder and full adder. I know the answer but how to get the gate diagram from the formula. Alloptical multiple logic gates with xor, nor, or, and nand functions using. So, take two copies of the 4 gate xor construction and hook them together, to get an 8 nand gate implementation of 3xor. Circuit diagram of a nand gate using transistors and resistors in the circuit diagram above you will notice that output is always high except when both transistors are biased. A truth table lists all possible combination of inputs and the corresponding outputs. The interconnection of gates to perform a variety of logical operation is called logic design. Therefore, this proposed alloptical logic gate can function as xor, xnor, nand and or gates for different input bpsk. Most logic gates have two inputs and one output and are based on boolean algebra.
When the inputs of both diodes of nand gate are connected to a high voltage level i. A low 0 output results only if all the inputs to the gate are high 1. In most of the cases, binary low is represented using the zero volts 0 v. Such a gate is said to be primitive or functionally complete. The behavior of logic gate with xor, xnor, nand and or functions for simulation is in accordance with table 3. Integrated circuits contain collections of gates suited to a particular purpose. Xor schematic using nmosfets and diodes is given below.
An xnor gate is made by considering the disjunctive normal form. Tamas kovacs thursday, august 19, 2004 i want it plant marwa aly monday, october 11, 2004 please provide us the logic circuit for implementing xor gate using nand and nor gate. In this schematic 4 diodes are used in a bridge configuration for sorting out input logic. The output of the xor operation is true only when the values of the. Another promising solution presented in ruzicka 2007 is a nand xor gate controlled by a control signal using nine transistors. Sep 07, 2017 according to many sources for instance wikipedia, its possible to obtain xor gate using 4 nand gates. We discussed about how to make xor and xnor gate using nand gate. As can be seen in the logic diagram below, the xor gate is built by combining three more simple gates, the or gate, the nand gate and the and gate to produce the desired result. The field distributions of logic gate at the wholec band with xor, xnor, nand and or functions are shown in fig.121 1142 202 172 1513 328 1377 1191 712 471 870 211 497 1420 102 905 46 776 844 1406 1348 885 950 1187 879 48 840 853 471 60 581 1030 167 1418 372 521 508 999 278 504 1480 87 316 367