Comparison between ttl and cmos logic families pdf

Ttl stands for transistor transistor logic, cmos stands for complementary metal oxide semiconductor and ecl stands for emitter coupled logic. Cmos and ttl are the two most widely used logic families. Pdf on apr 20, 2017, shree krishna khadka published comparison of. Each family has its own advantages and limitations. Chapter 2 digital circuits ttl and cmos based on chapter 3. They deliver speed and drive on a par with ttl, quashing worries about.

The simulation had been carried out at power supply voltage value of 3 v. I will just quote a part from difference between cmos and ttl. Susceptibility of integrated circuits to electrostatic. The 54hct74hct devices are primarily intended to be used to provide an easy method of interfacing between ttl compatible microprocessor and associated peripherals and bipolar ttl logic to 54hc74hc. Pdf comparison of logic families using nand gate editor. They deliver speed and drive on a par with ttl, quashing worries about highspeed systems built with cmos alone.

Ecl and gaas gates consume much more power than ttl or cmos gates, and cant be fabricated to the high level of integration that ttl or cmos can. Mar 12, 2020 i will just quote a part from difference between cmos and ttl. The lowlevel noise margin s l is the most critical value for all three logic families, ranging from 18. What is the definition of a ttl transistortransistor logic compatible signal. When cmos logic is expected to drive ttl logic, the cmos gate may not have the current capability to drive the ttl gate. Cmos chips are a lot more susceptible to static discharge compared to ttl chips. Interfacing logic familiesinterfacing logic families when using ttl logic to drive cmos logic the high level voltage of the ttl output must be increased with a pullup resistor. The effects of esd on various logic gates belonging to both transistortransistor logic ttl and complementary mos cmos logic families have been studied. Cmoslogic digital logic families electronics tutorial. These two logic families were not readily compatible. Difference between cmos and ttl compare the difference.

There are essentially two applications areas where a. For a cmos gate operating at a power supply voltage of 5 volts, the acceptable input signal voltages range from 0 volts to 1. The quick reference attributes charts on page 3may be a good. Cmos logic family has become the most widely used logic families due to its numerous advantages such as less power consumption and low noise during transmission levels. Logic signal voltage levels logic gates electronics textbook. Ttl vs cmos technology \\ comparison \\ interview questions. It was build in 1961 by james l bui and commercially used in logic design in 1963. For example, a certain amount of current is needed in order to operate correctly. There are different families of logic gates in digital logic design. Compare and contrast the 7400 series and 4000 series logic familes with reference to at least 5 characteristics e. Logic families and their characteristics website staff ui. As the cmos consists of the fets and the ttl circuits are made up of bjt, cmos chips are much faster and efficient. Ttl and cmos characteristics purpose logic gates are classified not only by their logical functions, but also by their logical families.

Many logic families were produced as individual components, each. There are essentially two applications areas where a designer will want to perform this interface. The graph provides a comparison of input and output io logic switching levels for the cmos, ttl, mixed cmos ttl, etl, btl, gtl, and low voltage glue logic families. Introduction and comparison of 74hct ttl compatible cmos logic. Compare it with the average propagation delay of a ttl gate e. The name is derived from the use of two bipolar junction transistors or bjts in the design of each logic gate. A two input gate will have two emitters and a four input gate will have four emitters.

To overcome the shortcomings of ttl gates more technologically advanced methodologies were designed for gates construction, such as pmos, nmos and the most recent and popular complementary metal oxide semiconductor type, or cmos. What are the basic differences between cmos and ttl. Ttl logic families free download as powerpoint presentation. Difference between ttl, cmos, ecl and bicmos logic families. You may wonder why the nand gate is so popular in the ttl logic families. The threshold level, logic level or transition point is shown to the left of the voltage range. Ttl logic switching levels and a comparison of the different logic families. For this course, we need to study only ttl and cmos mostly ttl. A ttl input signal is defined as low when between 0v and 0. Power, delay, and powerdelay products are some of the performance parameters considered for comparison between various logic families. Logic gates, esd stress modes, ttl, cmos, susceptibility. Its performance is a vast improvement over all other logic families. This page compares ttl vs cmos vs ecl logic families and mentions difference between ttl and cmos and ecl based on various parameters such as fanout,power consumption,noise immunity etc.

Cmos logic families many families of logic exist beyond static cmos comparison of logic families for a 2input multiplexer briefly overview pseudonmos differential cvsl dynamicdomino complementary passgate. The graph provides a comparison of input and output io logic switching levels for the cmos, ttl, mixed cmosttl, etl, btl, gtl, and low voltage glue logic families. Tis goal is to help designers easily find the ideal logic technology or function they need. The advantage of the cmos over the ttl chips is that the cmos has a higher density of logic gates within the same material. One major improvement was to combine cmos inputs and ttl drivers to form of a new type of logic devices called bicmos logic, of which the lvt and alvt logic families are the most important. There is a much higher density of the logic functions in a single chip in cmos as compared to the ttl. In the late 1960s, when the standard ttl family offered 20 ns gate delay and the cmos 4000 family had delays of 100 ns or more, mecl10k offered 1 ns.

When 5v supply is given to ttl and cmos ics, logic levels of ttl and cmos are different. Logic families are offered at every priceperformance node along with benchmark delivery, reliability, and. Bipolar transistor transistor logic ttl first introduced by in 1964 texas instruments ttl has shaped digital technology in many ways standard ttl family e. The comparison between ttl and cmos logic gates reveal that cmos devices are more susceptible to esd than ttl devices. Ecl is fastest logic family among all and this is due to. Carry lookahead adder working, circuit and truth table. The bicmos family has many members, including abt logic, alb logic, alvt logic, bct logic and lvt logic. Evaluation of logic families using nor and nand logic gates. These families are about twice as fast as hchct while maintaining backwards compatibility with their predecessors. Ttl transistortransistor logic uses a different type of transistor bipolar whereas cmos uses mosfets metal oxide semiconductor field effect transistor. Difference between ttl and cmos ics and how to choose.

A tabulation of the major logic families with relevant data is given. Transistortransistor logic first introduced by in 1964 texas instruments ttl has shaped digital technology in many ways one of the most widely used families for small and mediumscale devices rarely used for vlsi standard ttl family e. There are various logic families namely diode logic dl resistortransistor logic rtl diodetransistor logic dtl emitter coupled logic ecl logic families can be classified broadly according to the technologies they are built with transistortransistor logic ttl cmos logic ttl and cmos logic family is most widely used ic technologies. The other two families are for military and industrial application. Cmos is selected over nmos for the designing of an embedded system. All the common microprocessors, microcontrollers, and integrated circuits use cmos technology. What is the difference between ttl and cmos advantages of cmos over ttl. Cmos gate circuits have input and output signal specifications that are quite different from ttl. Cmos allows a much higher density of logic functions in a single chip compared to ttl. This document describes the main logic families and their characteristics. How can we compare and contrast ttl and cmos logic families. Although ics belonging to the same logic family have no special interface requirements, that is, the output of one can directly feed the input of the other, the same is not true if we have to interconnect digital ics belonging to different logic families. Logic signal voltage levels logic gates electronics.

These differences can cause problems when you connect a. Cmos vs ttl ttl stands for transistortransistor logic. Each ic family has its own characteristics, limitations and advantages. The output stage of most ttl logic is a totempole circuit. However, cmos power consumption increases faster with higher clock speeds than ttl does. I dont have the book and i dont remember anything else about it. Initially launched as straight 7400 series integrated circuits, this logic ic family has spawned many variants which has enabled it to remain in use until this day. Cmos complimentary mos cmos considerably lower energy consumption than ttl and ecl, which.

In any implementation of a digital system, an understanding of a logic elements physical capabilities and limitations, determined by its logic family, are critical to proper operation. Several new cmos families were introduced in the 1980s and the 1990s. A logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, usually with compatible logic levels and power supply characteristics within a family. Wh l i ttl nand i l h when at least one input to a ttl nand gate is low, the. Difference between ttl and cmos ics and how to choose between. Introduction and comparison of 74hct ttl compatible cmos. It is a logic family consisting completely of transistors.

In the present work, nand gate is implemented using rtl, dtl, ttl and cmos structures. There are cmos chips that have ttl logic and are meant as replacements for ttl chips. With respect to noise margins, hc devices feature significantly better performance than bipolar logic circuits. What are the basic differences between cmos and ttl signals. There is a big difference between the current that a ttl. To compare ttl and cmos, one must think about the points mentioned above. A ttl input signal is defined as low when between 0 v and 0. Ttl circuits consumes more power compared to cmos circuits at rest. Ttl outputs are typically restricted to narrower limits of between 0v and 0. Over the years, the most widely used overall family has been the 7400 series ics. Difference between cmos and ttl difference between. The set of logic gates constructed using coupled transistors and resistors are collectively known as ttl gate family. Logic selection guide how to use this guide the data on this page page 2give an historic overview of fairchilds available logic families. Cmos stands for complementary metaloxidesemiconductor whereas nmos is a negative channel metal oxide semiconductor.

How can we compare and contrast ttl and cmos logic. Cmos allows a much higher density of logic functio. The time interval between the instants when the input and output. Cmos circuits do not draw as much power as ttl circuits while at rest. Susceptibility of integrated circuits to electrostatic discharge. Hccmos has virtually the same speed and loaddelay variation as tlf51011 figure 1. Ttl circuits utilize bjts bipolar junction transistors while cmos circuits utilize fets field effect transistors. May 18, 2018 comparison and difference between the ttl logic family and cmos logic family which is one of the favourite questions for many interviewers related to electronics engineering posts. Hc, ls, als, s comparison of propagation delay vs load for a nand gate table i. Cmos and nmos are two logic families, where cmos uses both mos transistors and pmos for design and nmos use only field effect transistors for design. Two of the most recent and probably the most versatile are vhc very highspeed cmos and vhct very highspeed cmos, ttl compatible. Include a pin out diagram for the and logic function on ttl 7400 series and cmos 4000 series intergrated circuits.

Jan, 2006 what is the difference between ttl and cmos advantages of cmos over ttl. In fact logic gates can be implemented in pneumatic and hydraulic systems for special purpose applications in hazardous areas in petrochemical plants. Ttl transistortransistor logic families history and. Figure1 depicts ttl to cmos interfacing and cmos to ttl interfacing circuits. Logic families are sets of chips that may implement different. Difference between ttl cmos ecl ttl vs cmos vs ecl.

Difference between ttl and cmos electronics forums. The primary advantage of cmos chips to ttl chips is in the greater density of logic gates within the same material. Memories in digital electronics classification and characteristics. Uses much less power, can operate on a small battery for a year or so. Commercially it starts with the 74 series like the 7404, 74s86 etc.

The 4000a cmos family has been replaced by its highvoltage versions in the 4000b and 4000ub cmos families, with the former having buffered and the latter having unbuffered outputs. Boolean algebra all the laws, rules, properties and operations. All of these technologies were developed in the 1950s1960s and evolved over. Sep 29, 2012 cmos logic family has become the most widely used logic families due to its numerous advantages such as less power consumption and low noise during transmission levels. In computer engineering, a logic family may refer to one of two related concepts. Voltage levels range from 0 to vcc where vcc is typically 4. Comparing 7400 series to the 4000 series logic familes. Logic voltage thresholds for ttl, cmos, lvcmos, and gtlp. Comparison of typical ac performance of lsttl, sttl, alsttl and hccmos gates lsttl alsttl hccmos sttl units. Among the technologies discussed here are dl, rtl, dtl, ecl, ttl, cmos and bicmos. Logic voltage thresholds for ttl, cmos, lvcmos, and gtlp ic.

Comparison of digital logic families important for electronics dic paper mumbaiu b. Working voltage, maximum frequency, threshold voltage for ones and zeros, fanin, fanout, power consumption. The ttl family the input of a ttl logic gate is characterized by a multi emitter transistor. Ecl is fabricated with unsaturated logic and lowlevel differential drive. Als, as, f, ls, s, ttl logic guide introduction and contents todays applications are evolving with greater functionality and smaller size. Ecl is based on use of current steering switch realised using differential transistor pair. There have been many improvements in logical families such as ttl and cmos.