Nptel gate preparation using nptel content video lecture. The demultiplexer converts a serial data signal at the input to a parallel data at its output. Electrical characteristics of logic gates logic levels and noise margins, fanout, propagation delay, transition time, power consumption and powerdelay product. This page contains gate cs preparation notes tutorials on mathematics, digital logic, computer organization and architecture, programming and data structures, algorithms, theory of computation, compiler design, operating systems, database management systems dbms, and computer networks listed according to the gate cs 2020 syllabus. Jun 19, 2019 in this tutorial, we will have a brief introduction to logic gates. And, or, not, nand not and, nor not or, xor, and xnor not xor later building functions. The basic logic gates arethe inverter or not gate, the. A gate is an electronic device which is used to compute a function on a two valued signal. Since the logic gates themselves have delay, the change may happen with some delay. If the input is 0, it makes the output 1, and vice versa. The current drive of the transistor gatetosource voltage is reduce significantly as v. Share this article with your classmates and friends so that they can also follow latest study materials and notes on engineering subjects. Basically, all logic gates have one output and two inputs. In this article, you will find the study notes on logic families which will cover the topics such as integrated circuits, characteristics of digital circuits, logical families, digital ic terminology, dl, rtl, dtl and ttl.
Binary algebra, logic gates, digital integrated circuits, flipflops and sequential logic circuits, applications of logic circuits. How digital logic gates are built using transistors. The digital logic design notes pdf dld pdf notes book starts with the topics covering digital systems, axiomatic definition of boolean algebra, the map method, fourvariable map, combinational. Connection of the led at the output is optional which simply. Though primitive on their own, these logic gates can be strung together to form complex logical operations.
The demultiplexer is a combinational logic circuit designed to switch one common input line to one of several seperate output line the data distributor, known more commonly as a demultiplexer or demux for short, is the exact opposite of the multiplexer we saw in the previous tutorial. Although a knowledge of calculus will enhance the understanding of pid controls, it is not required in order to learn how to properly tune a pid. The basic logic gates arethe inverter or not gate, the and. For the love of physics walter lewin may 16, 2011 duration. Its outputs only depend on current inputs and not previous inputs. Diode logic gates use diodes to perform or and and logic functions as shown in the circuit diagram. In fact, most gates are implemented in solidstate ttl chips transistortransistor logic e. Logic gates actually look like weird bugs in real life.
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. 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. However, the diagrams we use are easier to understand. From switches to transistors, logic gates and logic circuits hakim weatherspoon cs 3410, spring 20 computer science cornell university see.
These are called logic gates and, or, not, nand, nor, xor, l i t b ilt i t i tlogic gates are built using transistors not gate can be implemented by a single transistor and gate requires 3 transistors transistors are the fundamental devices. Digital integrated circuits combinational logic prentice hall 1995 combinational logic. The circuit is called an inverter because it inverts the logic level of the input. A variety of names is used to label these two states.
Elaboration parse hdl program into standard form 2. Switching theory and logic design pdf notes stld pdf. Nsz fsg, uitm pahang lesson outline and gate or gate inverter and buffer nand nor gate exclusive or gate exclusive nor gate practical ttl and cmos gates 2 lesson outcomes at the end of this lesson, students should be able to. This subject includes number representation and computer arithmetic, combinational and sequential circuits, boolean algebra, and minimisation with a weightage of 78 marks. It is one of the important subjects of computer science engineering exam. Switching primitives and logic gates, logic families. It is an electronic circuit having one or more than one input and only one output. Were looking at logic states and were completing section 151. It is one of the important subjects of computer science engineering exam this subject includes number representation and computer arithmetic, combinational and sequential circuits, boolean algebra, and minimisation. Based on this, logic gates are named as and gate, or gate, not gate etc.
Digital logic gates the electrical circuits which perform logical operations are called gates. Not, and, or, and xor there are also other ones, such as nand, nor, and xnor that were not going to cover. Integrated circuits integrated circuits ics are chips, pieces of semiconductor material, that contain all of the transistors, resistors, and capacitors necessary to. Used to build logic functions there are seven basic logic gates. The symbols for these gates and their corresponding boolean expressions are given in table 8. Logic gates are the basic building blocks of any digital system. In other words, combinational logic gates do not have memory or storage. Jan, 2014 for the love of physics walter lewin may 16, 2011 duration. The three bestknown logic gates are the not, and, and or gates shown in. We will see the different logic levels in ttl circuits, cmos circuits, some simple logic gates like or, not, nand, and, etc. Classification of sequential circuits synchronous, asynchronous, pulse mode, the level mode with examples basic flipflopstriggering and excitation tables. Logic gates use switch behavior of mos transistors to implement logical functions. Both nand and nor gates can be used to make any other type of gate. Logic gates are the basic building block of digital circuits.
Other terms which are used for the true and false states are shown in the table. The simplest type of combinational logic design consists of inverters, and gates, and or gates. Digital electronics part i combinational and sequential logic. Introduction to digital logic basics hardware consists of a few simple building blocks. The basic logic gates arethe inverter or not gate, the and gate. The interconnection of gates to perform a variety of logical operation is called logic design. Logic gates not, or, and, nor, nand, xor, xnor gate, pdf. Srinivasan, department of electrical engineering, iit madras. Boolean operations and functions, algebraic manipulation, minterms and maxterms, sumofproducts and productofsum representations, functional completeness. Digital logic gate functions include and, or and not. From transistorsto logic gates and logic circuits prof. Digital electronics part i combinational and sequential. V s will initially charge up quickly, but the tail end of the transient is slow.
A binary operator on a set s is said to be associative whenever. Digital devices operate on binary values so there are only two allowable digital states. Digital circuits are part of any electronic design today. The outputs of the gates assume at all times the value of the boolean function, implemented by the circuit. In sequential logic the output of the logic device is dependent not only on the present inputs.
Here you can download the free lecture notes of digital logic design pdf notes dld notes pdf materials with multiple file links to download. Static logic circuits are those which can hold their output logic levels for indefinite. Logic minimisation any boolean function can be implemented directly using combinational logic gates however, simplifying the boolean function will enable the number of gates required to be reduced. Digital logic is rooted in binary code, a series of zeroes and ones each having an opposite value. Switching theory and logic design pdf notes stld pdf notes. Introduction to logic gates not, and, nand, or, nor. We provided the download links to digital logic design books pdf download b. Guru jambheshwar university of science and technology, hisar. Boolean expressions are written by starting at the leftmost gate, working toward the final output, and writing the expression for each gate. Given a switching a function, generate the set of prime implicants using tabular method and minimize the function. Physical resynthesis transform circuit when placing.
Digital logic design pdf notes dld notes pdf eduhub sw. Calculating the logical effort of gates where c b is the combined input capacitance of every signal in the input group b, and c inv is the input capacitance of an inverter designed to have the same drive capabilities as the logic gate whose logical effort we are calculating. Logic gates digital circuit that either allows a signal to pass through it or not. Another class of digital circuits, which can be built with gates, have memory. The karnaugh map provides a method for simplifying boolean expressions it will produce the simplest sop and pos expressions works best for less than 6 variables similar to a truth table it maps all possibilities a karnaugh map is an array of cells arranged in a special manner the number of cells is 2n where n number of variables a 3variable karnaugh map. Minimize the given switching functions in sop and pos forms using kmap.
This creates trees of gates that depend on each other. 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. Not, or, and and gates are the basic types of gates. A logic gate is a circuit with one or more input voltages but only one output voltages. Sequential logic so far we have investigated combinational logic for which the output of the logic devicescircuits depends only on the present state of the inputs. This system facilitates the design of electronic circuits that convey information, including logic gates. The data distributor, known more commonly as a demultiplexer or demux for short, is the exact opposite of the multiplexer we saw in the previous tutorial the demultiplexer takes one single input data line and then switches it to any one of a number of individual output lines one at a time. Gate cs topic wise preparation notes geeksforgeeks. The minimization will result in reduction of the number of gates resulting from less number of terms and the number of inputs per gate resulting from less number of variables per term the minimization will reduce cost, efficiency and power consumption. Shown here are example of truth tables for logic gate with 2, 3 and 4 inputs. The proposed course on digital circuits will cover all the fundamental concepts in digital design.
Logic optimization minimize costmaximize performance 3. This is called boolean logic in a circuit schematic each logic gate is represented by a different picture, like the ones shown below. Digital logic is the representation of signals and sequences of a digital circuit through numbers. Some logic gates like not gate or inverter has only one. Introduction logic gates process signals which represent true or false. Anne bracy cs 3410 computer science cornell university the slides are the product of many rounds of teaching cs 3410 by professors weatherspoon, bala, bracy, and sirer. All data manipulation is based on logic logic follows well defined rules. Logic functions implemented using cmos transmission gates provide a moderate improvement in area and speed over logic gate implementations. Combinational logic modules and their applications. Lecture notes for digital electronics university of oregon.
Boolean analysis of logic circuits boolean expression for a logic circuit. Boolean algebra and logic gates the most common postulates used to formulate various algebraic structures are. An output of one logic gate can be an input to another logic gate. Cmos produces inverting logic cmos gates are based on the inverter outputs are always inverted logic functions e.
Vajpeyi department of physics, indian institute of technology guwahati, india 1. Digital logic is the basis of electronic systems, such as computers and cell phones. Algebraic manipulation as seen in examples karnaugh k mapping a visual approach. Stroud combinational logic design 106 8 functionally complete set of gates a za the nand gate is functionally complete.
1150 1278 720 1140 280 102 839 340 421 517 1251 440 1324 498 1423 460 1178 1193 1029 1212 415 1316 926 17 1136 228 964 1442 368 15 1546 1233 1031 175 478 579 1566 194 909 815 1392 807 440 199 981 976 1468