These gates are the and, or, not, nand, nor, exor and exnor. Nand and nor are universal gates any function can be implemented using only nand or only nor gates. Realization of boolean expression using nandnor gates gate. The output of this gate is exactly similar to that of a single or gate. Request pdf on jul 1, 2017, zhongqin fang and others published reconfigurable optical logic gate of and, or, nand and nor based on polarization modulation with direct detection find, read and. A full adder circuit is an arithmetic circuit block that can be used to add three bits to produce a sum and a carry output. Nand and nor gates are called as universal gates as they can be used to create all other logic gates. This article covers two input logic gates, demonstrates that the nand gate is a universal gate, and demonstrates how other gates are universal gates that can be used to construct any logic gate. Basic logic gates and, or, and not gates objectives. Digital electronicslogic gateslogic nand wikibooks, open. See the newest logic products from ti, download logic ic datasheets, application notes, order free samples, and use the quick search tool to easily find the best logic solution. This is because, this gate can function as any of the basic logic gates by just making some changes at its input side.
Jan, 2014 for the love of physics walter lewin may 16, 2011 duration. 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. In the field of digital electronic circuits, this implies that we can implement any boolean function using just nand gates. A not gate is made by joining the inputs of a nand gate together. So it is clear that during the operation of nand gate, the inputs are first going through and gate and after that, the output gets reversed, and. We have seen how nand gate can be used to make all the three basic gates by using that alone. Hence a user can build any combinational circuit with the help of only nand gates or only nor gates. In fact, most gates are implemented in solidstate ttl chips transistortransistor logic e. The ability for a single gate type to be able to mimic any. Watch this video to learn more and see the interesting practical. Each output and output of a logic gate is represented by binary conditions 0 low and 1 high. At vb vm, only m4 is conducting current only half the current. Between the two levels, we are using negative logic, and the bubbles are used to denote this.
Digital logic gates nand and nor are called universal logic gate because we can construct all other logic gates using nand gate or nor gate alone. By default, any inputs that are left unconnected are ignored thats if the input truly has nothing attached to it, not even a wire. Series connection of pmos increases the resistance of the circuit and. Most logic gates have two inputs and one output and are based on boolean algebra. Apr 25, 20 with nor gate also one can proceed with the same assumptions as above just by interchanging nand with nor and sop with pos. Neural representation of and, or, not, xor and xnor logic. How to draw a nand gate using only nor gates quora. And vs nand vs or vs nor gates and,nand,or,nor 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. Logic gates are electronic circuits which perform logical functions on one or more inputs to produce one output. By contrast, the or operator is monotonic as it can only change low to high but not vice versa.
The nand boolean function has the property of functional completeness. Now we will go over how to build an and gate from nand gates. The outputs of all nand gates are true if any of the inputs are false. This circuits truth table, then, is equivalent to that of the nor gate. In practice, this is advantageous since nand and nor gates are economical and easier to fabricate and are the basic gates used in all ic digital logic families.
We know that all boolean functions can be expressed in terms of and, or and not. This video takes the viewers, step by step to four different derived gates, i. Simple gates with 60 input capacitance of 60 unitsized transistors. Here i have considered all inputs to be provided in both complemented and uncomplemented form but to get an actual number of gates we have to consider nand as an inverter to get every input in complemented form which. Nand gates are one of the two basic logic gates the other being nor logic from which any other logic gates can be built.
That using a single gate type, in this case nand, will reduce. Cmos static nand gate n second switching condition. It produces a 1 output only when even number of 1 is present at the input. Although and,or and not are basic gates but each of their functionality can be derived using nand and not as well. Logic gate actually the term logic is applied to digital circuits used to implement logic functions.
Below is a cool chart that shows how to turn a nand gate into the other kinds of gates. Dec 21, 2014 how to prove that a nand gate is a universal gate by admin in digital electronics, electronics on december 21, 2014. Now let us see how each logic gate can be created with nand and nor gates. The above diagram is of an or gate made by only using nor gates. Nand and nor gates would both have a logical effort of 1. In ttl ics using multipleemitter transistors, it also requires fewer transistors than a nor gate. So the circuit of figure 159 is interpreted in mixed logic. Today, integrated circuits are not constructed exclusively from a single type of gate. To see this, lets show that nand gates can be used to implement not, and and or. Mostly, we prefer nand gates over nor gates for designing the other basic logic gates. A nor gate is logically an inverted or gate implementation of not gate using nand not made by joining the inputs of a nor gate.
The symbol is an and gate with a small circle on the output terminal. Hence a nor gate is made up from a or gate which is followed by an inverter. How a nand gate can be used to replace an and gate, an or gate, or an inverter gate. The gate is either a nand or an ex or gate b nor or an ex nor gate c an or or an ex nor gate d an and or an exor gate. In most of the cases, binary low is represented using the zero volts 0 v. Basic logic gates using nand gate not, or, and gates. Nand and nor gates are arguably more flexible than and and or gates because you can also turn them into inverters. Logic design unit 7 multilevel gate circuits sauhsuan wu two of the most commonly used circuits are the nand nand and the nor nor procedure for designing a min 2level nand nand circuit find a minimum sop for f draw the corresponding twolevel and or circuit replacing all gates with nand gates. Lets see why these are preferred and how we can design other gates by using nand gate. Universal gate nand i will demonstrate the basic function of the nand gate. Proof for nand gates any boolean function can be implemented using and, or and not gates. Nand flash density for any given lithography process, the density of the nand flash memory array will always be higher than nor flash. The word nor gate is just an short form of the not and or gate combination. Nand and nor are called universal gates because all the other gates like and,or,not,xor and xnor can be derived from it.
Nor function implementation nand gates can implement a simplified sum of products form. For example, the function notx may be equivalently expressed as nand x,x. The first part is an and gate and second part is a dot after it represents a not gate. There are many articles about how nand and nor are universal gates, but many of these articles omit other gates that are also universal gates. This means, any boolean expression can be reexpressed by an equivalent expression utilizing only nand operations. Two input nand gate nand gate is known as universal gate as it can be used alone to implement any gate operation. The operation is the same as for the two input nand gate, satisfying all three basic rules.
Patel college of engineering and technology subject. Digital circuitsnand logic wikibooks, open books for an. An entire processor can be created using nand gates alone. As v a and v b both are low, both the pmos will be on and both the nmos will be off. Nand and nor gates are easier to fabricate with electronic components. How a logic circuit implemented with aoi logic gates can be reimplemented using only nand gates. To demonstrate the operation and characteristics of nand and nor gates and to show how any of these gates can be used to perform any of the three basic logic functions. 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. In electronics, a logic gate is an idealized or physical device implementing a. Nor flash memory technology overview page 3 nor vs. Nand and nor are universal gates university of iowa. For example, it is possible to build a circuit exhibiting the or function using three interconnected nand gates. So if and, or and not gates can be implemented using nand gates only, then we prove our point.
This is because any other logic gate on the planet can be made from the right combination of nand gates. Jan 04, 2020 now we will look at the operation of nor gates and nand gates as universal gates nand gate as universal gate. An inverter can be made from a nand gate by connecting all of the inputs together and creating, a single input as shown below. Normally invertors connected directly to input variables are not counted as a level in a circuit terminology 1. Basic electronics tutorials about universal logic gates and complete sets of logic to realise any other boolean function or logic gate with nand and not being.
So any boolean function can be implemented with nandnor gates alone. Continuing the process, the nand gate can be further extended to more three inputs as well. So it is clear that during the operation of nand gate, the inputs are first going through and gate and after that, the output gets reversed, and we. Connect the inputs to two switches connect the not gate input to one switch b. Nor is a functionally complete operationnor gates can be combined to generate any other logical function. A logic gate is a building block of a digital circuit. Universal logic gates and complete sets electronicstutorials. Verification and interpretation of truth tables for and, or, not, nand, nor exclusive or exor, exclusive nor ex nor gates apparatus. The nand and nor gates are called as universal gates, because it is possible to implement any boolean expression with the help of only nand or only nor gates. Now we will look at the operation of nor gates and nand gates as universal gates nand gate as universal gate. The figure2 depicts nand logic gate symbol and table2 below mentions truth table of nand gate. Logic gates and truth table and, or, not, nor, nand, xor. You will be able to prove the universality of nand and nor gates. So nand not and simply means that a nand gate performs the opposite function to.
The output of a nor gate is true all of its inputs are false. When all the input combinations of a logic gate are written. Logic gates and, or, not, nor, nand, xor, xnor gates. In order to turn this nor gate circuit into an or gate, we would have to invert the output logic level with another transistor stage, just like we did with the nand toand gate example. Universal gates in digital electonics nand and nor. Used to build logic functions there are seven basic logic gates. It produces a 1 output only when its two inputs are equal i. The nand gate is just a combination of the expression not gate as well as and gate. All of the sizing calculations in this monograph compute the input capacitance.
So the circuit of figure 21 is interpreted in mixed logic. However, modern integrated circuits are not constructed exclusively from a single type of gate. An or gate followed by a not circuit makes it a nor gate. Recognise common 74 series ics containing standard logic gates. Convert all and gates to nand gates with andinvert symbols 2. Calculating the logical effort of gates 40 20 a x 30 30 30 30 x a b 48 48 12 12 a b x figure 4. Now lets understand how this circuit will behave like a nand gate. Gate universality logic gates electronics textbook. Very quickly, below are the symbols, boolean expression and truth table of nand and nor gates. 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.
Several kinds of digital logic circuits are the basic elements that form the building blocks for such complex digital system as the. And, or, not, nand not and, nor not or, xor, and xnor not xor later building functions. The nand gate is a universal gate because it can be used to produce the not operation, the and operation, the or operation, and the nor operation. The circuit output should follow the same pattern as in the truth table for different input combinations. The nand gate has the property of functional completeness, which it shares with the nor gate.
Universal gate nand universal gate nand this presentation will demonstrate the basic function of the nand gate. At the input side and also at the output side, we are using positive logic, and the absence of bubbles indicates this. The noninverting gates do not have this versatility since they cant produce an invert. Logic gates not, or, and, nor, nand, xor, xnor gate, pdf. For the following logic gates, verify the logic operation each gate performs. Like nor gates, nand gates are socalled universal gates that can be combined to form any other kind of logic gate. It is referred to as the universal logic gate chip. Va vdd and vb switches from 0 to vdd at vb vm, the current through m1 and m2 is higher than when va vb since the gate voltage on m1 is now vdd and its vds1 must be smaller vgs2 is larger. The logic operations and, or and not can be obtained with nand gates as. The importance of nand nand gates are considered to be the universal gate, because any other gate can be synthesized eve engels, 2006 slide 22 of 20 using nand. Aug 04, 2015 the above drawn circuit is a 2input cmos nand gate. The output of a logic gate is 1 when all its input are at logic 0. In theory, the highest density nand will be at least twice the density of nor, for the same process technology and chip size. That using a single gate type, in this case nand, will reduce the number of integrated circuits ic required to implement a.
A nor gate sometimes referred to by its extended name, negated or gate is a digital logic gate with two or more inputs and one output with behavior that is the opposite of an or gate. A universal gate is a gate which can implement any boolean function without need to use any other gate type. The nand gate and the nor gate can be said to be universal gates since combinations of them can be used to accomplish any of the basic operationsand can thus produce an inverter, an or gate or an and gate. In addition to and, or, and not gates, other logic gates like nand and nor are also used in the design of digital circuits. Design of basic logic gates using nor gate not, or and. Hence the nand gate is made up of and gate which is followed by an inverter. At any given moment, every terminal is in one of the two binary conditions false high or true low. Depending on the context, the term may refer to an ideal logic gate, one that has for. From the diagram, the nor gate is 1 only if both inputs are 0. Due to this property, nand and nor gates are sometimes called universal gates. Ttl nor and or gates logic gates electronics textbook. Logic gates digital circuit that either allows a signal to pass through it or not. Comparative study of various gates based in different.
As a nor gate is equivalent to an or gate leading to not gate, this automatically sees to the or part of the nor gate, eliminating it from consideration and leaving only the not part. The twoinput truth table for the gates is the following. Reconfigurable optical logic gate of and, or, nand and nor. Nand gate and nor gate can be used as universal gates because all the basic logic gates can be realized using nand or nor alone as detailed below. In fact, all boolean functions can be expressed in terms of either nand gates only, or nor gates only. To build an inverter, you can use nand or nor gates as follows. Apr 11, 2016 logic gates and nand and nor univarsal gates 1. Once you have inverters, you can basically create any gate you want.
Pdf implementation of not, nand and nor gate mujtaba. They are most widely used in all ic digital families. Two of the input variables and represent the two significant bits to be added and the third input represents the carry from the previous lower significant position. Nand and nor gates can be used to realize all possible combinational logic functions. What is logic gate and, or, xor, not, nand, nor and xnor. Digital systems are said to be constructed by using logic gates. The output of a nor gate is logic 1 when all its inputs are logic 0. That is, given enough gates, either type of gate is able to mimic the operation of any other gate type. The universality of the nand and nor gates means that they can be used as an inverter and the combinations of nand nor gates can be used to implement the and, or, and all other logic operations. If one or more of a nor gate s inputs are true, then the output of the nor gate is false. Verify the functionally of the nand and nor gates by developing their truth table. Sep 18, 2014 proof for nor gates like nand gates, nor gates are socalled universal gates that can be combined to form any other kind of logic gate. The and, or, nand, and not gates each compute the respective function of the inputs, and emit the result on the output. Convert all or gates to nand gates with invertor symbols 3.