The inputs and outputs we discuss in logic gates are digital and will either be on or off, a 1 or a 0, true or false, 5v or 0v. When drawing a truth table, the binary values 0 and 1 are used. Nptel courses in engineering, science, management, humanities and social sciences. The relationship between the input and the output is based on a certain logic. Determine the output of the circuit for that random pattern as input. Other terms which are used for the true and false states are shown in the table.
Design of basic logic gates using nand gate there are mainly three types of logic gate named and, or and not gate. In doing so, we can abstractly think of electronic signals within a digital circuit as being either high or low i. Building functions from logic gates weve already seen how to implement truth tables using and, or, and not an example of combinational logic. Combinational logic modules and their applications. Some logic gates like not gate or inverter has only one. Nptel gate courses for mechanical engineering online video.
He was born in lincoln, england and he was the son of a shoemaker. Extract for each of the gates the truth table from the simulation waveforms. Roychoudhury, department of computer science and engineering,iit kharagpur. In this the variable permitted to have only values true offalse usually written as 1 or 0. In 1973 famous international business machines ibm researcher bennett 15, incidentally invented quantum cryptography and quantum teleportation. Note there are no constraints on the number of gate inputs. A combinational logic expression is a mathematical formula which is. Srinivasan, department of electrical engineering, iit madras. We provided the download links to digital logic design books pdf download b. Identify the types of logic gates which do the following there is more than one type of gate for each of the following rules. Nptel gate preparation using nptel content video lecture. Binary systems, boolean algebra, logic gates, analysis or design of combinatorial circuits, synchronous sequential logic, registers, counters and memory, laboratory experiments in digital circuits and logic logic design, contemporary logic design, switches.
Digital devices operate on binary values so there are only two allowable digital states. Logic gates are constructed from transistors, which are analog switches. The output of an and gate assumes 1, only if all the inputs assume 1. For example, if you have a fence, you install a gate.
Verify its operation by completing a voltage truth table for the gate. Learn for free, pay a small fee for exam and get a certificate. You can now walk to the gate, open it and then walk through. From switches to transistors, logic gates and logic circuits hakim weatherspoon cs 3410, spring 20 computer science cornell university see. Share this article with your classmates and friends so that they can also follow latest study materials and notes on engineering subjects. Shown here are example of truth tables for logic gate with 2, 3 and 4 inputs.
Number of gate inputs and outputs, gio more accurate bigger gates take up more area performance analysis worst case path from inputs to outputs. The basic logic gates are classified into seven types. This is an inverter gate, so named because its output is always the opposite inverted state as the input. Indian institute of technology, kharagpur, is all set to conduct graduate aptitude test in engineering gate for the year 2014. Based on this, logic gates are named as and gate, or gate, not gate etc.
The interconnection of gates to perform a variety of logical operation is called logic design. A binary operator on a set s is said to be associative whenever. Aim to study about logic gates introduction logic gates are related with boolean algebra, which differ from both ordinary and binary algebra. Binary logicdealing with true and false comes in handy to describe the behaviour of these circuits. Digital systems design nptel online videos, courses iit. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses, youtube iit videos nptel courses. The three bestknown logic gates are the not, and, and or gates shown in. A variety of names is used to label these two states. Thus operation of an and gate is based on the rule. Logic gates digital circuit that either allows signal to pass through it or not used to build logic functions seven basic logic gates. Proof for nand gates any boolean function can be implemented using and, or and not gates. Digital systems design nptel online videos, courses.
Srinivasan department of electrical engineering, iit madras. The circuit is called an inverter because it inverts the logic level of the input. In fact, most gates are implemented in solidstate ttl chips transistortransistor logic e. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel. Lab 1 part 2 identify the 7400 series ttl gates and look up their data sheets. Access the previous years gate question papers from here. The basic logic gates arethe inverter or not gate, the. Use 5 v for a high input and 0 v ground for a low input. For the love of physics walter lewin may 16, 2011 duration. So if and, or and not gates can be implemented using nand gates only, then we prove our point.
Electrical characteristics of logic gates logic levels and noise margins, fanout, propagation delay, transition time, power consumption and powerdelay product. Were looking at logic states and were completing section 151. 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. Logic gates are the basic building block of digital circuits. Digital systems design digital systems design lecture series on digital systems design by prof. It is an electronic circuit having one or more than one input and only one output. Jun 19, 2019 in this tutorial, we will have a brief introduction to logic gates. The basic logic gates arethe inverter or not gate, the and gate. The above said logic gates can be classified into following categories. Not, and, or, and xor there are also other ones, such as nand, nor, and xnor that were not going to cover.
Describe in your lab report each of their functions. Also show their logic symbol, use the function in an equation and show the truth table for one gate in each of the integrated circuits. Basically, all logic gates have one output and two inputs. Is it advisable to watch nptel lectures for gate mechanical. Introduction to logic gates not, and, nand, or, nor. Logic gates sometimes have different logical efforts for different inputs. Aim to study about logic gates introduction logic gates are. We can control the behavior of a gate, for instance, by putting a lock on it. Setup in the scf file the input signals as shown below and draw the output f as obtained from simulation. Admission are offered to postgraduate programmes in iits. The basic logic element the basic logic element or gate is an electronic device that has one or more digital inputs and one digital output. Not, or, and and gates are the basic types of gates. Can implement with multiple twoinput gates, or with single cmos circuit.
These transistors can be forced to operate in two modes, namely on or off. Logic gates not, or, and, nor, nand, xor, xnor gate, pdf. Logic synthesis methods have been developed for reversible circuits, 14. Digital logic gates the electrical circuits which perform logical operations are called gates. And, or, not, nandnot and, nornot or, xor xnornot xor 9 did you know.
Nptel provides elearning through online web and video courses various streams. Question 1 identify the type of logic gate shown in this schematic diagram, and explain why it has the name it does. In this example you are the input into the gate and the gate outputs you into the yard. Write a logic function that is true if and only if x, when interpreted as an unsigned binary number, is greater than the number 4. A gate is an electronic device which is used to compute a function on a two valued signal. Number of gates in worst case path from input to output, gdel.
Electrical engineering digital integrated circuits nptel. And gate, or gate, xor gate, nand gate, nor gate, xnor gate and not gate. All the logic gates have two inputs except the not gate, which has only one input. All of the logical gate functions, as well as the boolean relations discussed in the next section, follow from the truth tables for the and and or gates. Take fault from the fault list and modify the boolean functionally of the gate whose input has. National programme on technology enhanced learning nptel, offers free coaching for gate 2014 entrance exam preparation online. Logic designer frequently use nand and nor gates because. I referred to nptel lectures only when i needed to clear the concept of some topics, which i was unable to understand through the. Vajpeyi department of physics, indian institute of technology guwahati, india 1. Logic gates are the basic building blocks of any digital system. This is called boolean logic in a circuit schematic each logic gate is represented by a different picture, like the ones shown below. A logic gate is a circuit with one or more input voltages but only one output voltages. Nand and nor are universal gates any function can be implemented using only nand or only nor gates. Additional properties of xor xor is also called modulo2 addition.
Logic gates 4 oo software design and construction 2input logic gate hierarchy it is sensible to view each of the 2input logic gates as a specialized subtype of a generic logic gate a base type which has 2 input wires and transmits its output to a single output wire. Capital letters are normally used to make it clear that the term refers to a logic gate. Jan, 2014 for the love of physics walter lewin may 16, 2011 duration. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses. Digital logic circuits handle data encoded in binary form, i. Boolean algebra and logic gates the most common postulates used to formulate various algebraic structures are. If the input is 0, it makes the output 1, and vice versa. The second level is one 2input nand gate using invertor. Logic gates pdf 74p logic gates pdf 74p logic gates pdf 74p currently this section contains no detailed description for the page, will update this page soon. Nptel, online courses and certification, learn for free.
We will see the different logic levels in ttl circuits, cmos circuits, some simple logic gates like or, not, nand, and, etc. In fact, most gates are implemented in solidstate ttl chips transistortransistor logic. B a when control is high b a when control is low b a when control is high b a when control is low also, explain how an understanding of this can be helpful in troubleshooting faulted logic gates. Digital circuits and systems nptel online videos, courses. It will primarily focus on the prescribed gate syllabus for electronics and communication engineering ece specialization. Combinational logic circuit output depends only on the current inputs stateless sequential logic circuit output depends on the sequence of inputs past and present. Though primitive on their own, these logic gates can be strung together to form complex logical operations. Nptel offers free online coaching for gate 2014 exam. Sep 01, 2015 national programme on technology enhanced learning nptel, offers free coaching for gate 2014 entrance exam preparation online.