Directcoupled transistor logic dctl is similar to resistortransistor logic rtl but the input transistor bases are connected directly to the collector outputs without any base resistors. Jan 16, 2020 dtl ttl ecl mos cmos pdf evolution of ttl family. 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. Is the fastest logic family and has the lowest propagation delay. Logic families and their characteristics website staff ui. Saturation in ecl is avoided by using the bjt differential pair as a current switch. The quick reference attributes charts on page 3may be a good. Firstly, the circuit inside the dotted box is a voltage reference circuit providing a reference voltage at the base of t2. Typical propagation delays 1ns and below ecl noise margins are very low 150mv typ fanout is high 25 power dissipation remains. If you mix logic families the noise margin will need to be recalculated using the noise margin equation listed above.
Logic guide introduction and contents todays applications are evolving with greater functionality and smaller size. Current switching ecl is also vee sometimes called current. And8020d termination of ecl devices with ef emitter. Digital logic circuits are manufactured depending on the specific circuit technology or logic families. Unfortunately, dctl has much smaller signal levels, has more. In electronics, emittercoupled logic ecl is a highspeed integrated circuit bipolar transistor. Logic families discussed in the chapter include transistor transistor logic ttl, metal oxide semiconductor mos logic, emitter coupled logic ecl. One example is the philips norbits family of logic building blocks. The digital ics are designed using any of either bipolar devices or mos or a combination of both. New technologies are continually being developed in an effort to improve the logic. Logic families logic families are sets of chips that may implement different logical functions, but use the same type of transistors and voltage levels for logical levels and for the power supplies. Ecl uses an overdriven bjt differential amplifier with singleended input and limited emitter current to avoid the saturated fully on region of operation and its slow turnoff behavior. If either one of them is high 700 mv, then the or output is high, and the nor output is low. Each family has its own advantages and limitations.
Ecl logic has the capability of significantly reducing the clock skew of a system over an equivalent design utilizing cmos or ttl technologies. Logic families significance and types of logic families. The first kind of logic families is bipolar families. It mentions ecl advantages and ecl disadvantages over ttl and cmos. The first ecl logic family to be available in integrated circuits was introduced by motorola as mecl in 1962. Extension of mos inverter concepts to nor and nand gate is very simple. Emittercoupled logic ecl based on bipolar transistors, but removes problems of storage time by preventing the transistors from saturating. Ttl stands for transistor transistor logic, cmos stands for complementary metal oxide semiconductor and ecl stands for emitter coupled logic. 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. Logic selection guide how to use this guide the data on this page page 2give an historic overview of fairchilds available logic families. Jan 16, 20 ecl is non saturated digital logic family. Ttl transistortransistor logic families history and.
The storage time is eliminated as the transistors are used in difference amplifier mode and are never driven into saturation. The concept was later refined by motorola and others to produce the still popular 10k and 100k ecl families. The table also shows that the noise margin does not really get smaller as the voltage is reduced or as the logic family changes. As the current is steered between two legs of an emittercoupled pair, ecl is sometimes called. This is a noror gate using emittercoupled logic, a highspeed type of logic using transistors. Integrated circuits integrated circuits ics are chips, pieces of semiconductor material, that contain all of the transistors, resistors, and capacitors necessary to. Digital logic families in digital designs, our primary aim is to create an integrated circuit ic.
Fill in the banks of the statements below concerning the following logic families. Ecl s major disadvantage is that each gate continuously draws current, which means that it requires and dissipates significantly more power than those of other logic families, especially when quiescent. These families vary by speed, power consumption, cost, voltage. In computer engineering, a logic family may refer to one of two related concepts. This page covers advantages and disadvantages of ecl. Characteristics of logic families in digital electronics. The ecl family, ecl is also known as currentmode logic cml, was invented by ibm as current steering logic for use in the transistorized ibm 7030 stretch computer, where it was implemented using discrete components. This document describes the main logic families and their characteristics. Jan 26, 2018 for the love of physics walter lewin may 16, 2011 duration. These families are extremely fast, offering propagation delays as short as 1 ns. The ecl emitter coupled logic families, originated in the late 1950s and remain the fastest chips available, but consume more power, and because they use a negative power supply of. Logic families are sets of chips that may implement different logical functions but use the same type of transistors and voltage levels for logical levels and for the power supplies. Current switching ecl is also vee sometimes called currentmodelogic cml5. Within each logic family are one or more logic series that have distinctive characteristics, relative to other series within the same logic family.
Emitter coupled logic the main specialty of ecl is that it is operating in active region than the saturation region. The pmos and i2l logic families were used for relatively short periods, mostly in special. Emittercoupled logic ecl is the fastest logic circuit family available for. The basics of emittercoupled logic technical articles. Instead, it has a small voltage swing, less than a volt, and it internally switches current between two possible paths, depending on the output state. Also note that the noise margin in cmos is higher than the noise margin in ttl for 5 volt logic.
A circuit configuration or arrangement of the circuit elements in a special manner will result in a particular logic family. The equivalent of emittercoupled logic made out of fets is called sourcecoupled logic scfl. The equivalent of emittercoupled logic made from fets is called sourcecoupled logic scfl. Ecls major disadvantage is that each gate continuously draws current, which means that it requires and dissipates significantly more power than those of other logic families, especially when quiescent. Emittercoupled logic ecl based on bipolar transistors, but removes problems of storage time by preventing the transistors from saturating very fast operation propagation delays of 1ns or less high power consumption, perhaps 60 mwgate low noise immunity of about 0. Dc termination analysis vt rt rt rt rt vt1rt vt2 external internal near standard pair far standard pair far standard pair vee rt rt r t vt1 vt2 vee. Emitter coupled logic non saturated logiccurrent mode logic. Different gates are constructed using integrated circuits. In electronics, emittercoupled logic ecl is a highspeed integrated circuit bipolar transistor logic family. Digital mos circuits can be classified into two categories. Lvds, cml, ecldifferential interfaces with odd voltages. As you can see in the figure, the emitters of the transistors q1 and q2 are coupled together.
Each ic family has its own characteristics, limitations and advantages. For example, in the ttl logic family, there are several logic series. Consequently, dctl gates have fewer components, are more economical, and are simpler to fabricate onto integrated circuits than rtl gates. Integrated injection logic i2l the families rtl, dtl, and ecl were derived from the logic circuits used in early computers, originally implemented using discrete components. Difference between ttl cmos ecl ttl vs cmos vs ecl.
There are different families of logic gates in digital logic design. The logic families which fall under the first kind are called bipolar families, this include diode logic dl, emitted coupled logic ecl, resistor transistor logic rtl, diode transistor logic dtl, transistor transistor logic ttl. Termination of ecl devices with ef emitter follower output structure prepared by. Ecl emittercoupled logic bjts operating in unsaturated mode i. Unlike the other logic families in this chapter, ecl does not produce a large voltage swing between the low and high levels. Emitter coupled logic non saturated logic current mode logic. Nov 07, 2017 prebook pen drive and g drive at teacademy. Digital logic families digital logic has evolved over the years and this process has led to the development of a variety of families of digital logic integrated circuits. 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. Paul shockman on semiconductor logic applications engineering contents of application note introduction. Logic families are offered at every priceperformance node along with benchmark delivery, reliability, and worldwide support.
Rtlresistor transistor logic dtldiode transistor logic ttltransistor transistor logic eclemitter coupled logic cmoscomplementary metal. Which logic family has the highest power dissipation per gate a. Rtl, dtl, ttl, ecl to 7400 with its modern low voltage variants. Internal temperature and voltage compensated bias network. The recent invention of magnetoresistive bipolar spintransistors makes possible the creation of new spintronic logic families. Therefore, gates are grouped into logic families such that all gates in a logic family obey the static discipline when used with other gates in the family.
Mos metal oxide semiconductor field effect transistors. Ecls major disadvantage is that each gate continuously draws current, which means it requires and dissipates significantly more power than those of other logic families, especially when quiescent. Today the most widely used is something called cmos, complementary metal oxide semiconductor. Emittercoupled logic is based on the use of the currentsteering switch introduced in section 15. Emittercoupled logic ecl emittlercoupled logic ecl was invented in 1956 by hannon s. There have been many improvements in logical families such as ttl and cmos. This meant that interoperation between ecl and other logic families, such as the popular ttl family, required additional interface circuits. Standard ttl 74 xxxll, low power ttl 74lxx low power schottky. The newest ecl family, eclinps literally, ecl in picoseconds, offers maximum. In ecl technology a logic 0 is defined as having a larger negative voltage than a logic 1. Ecl emittercoupled logic ecl based on bjt, but removes problems of delay time by preventing the transistors from saturating very fast operation propagation delays of 1ns or less high power consumption, perhaps 60 mwgate logic levels. Emittercoupled spintransistor logic request pdf researchgate. The first ecl logic family was introduced by general electric in 1961. Such a switch can be most conveniently realized using the differential pair.
Lvds, cml, ecldifferential interfaces with odd voltages by john goldie, applications manager there are many differential signaling technologies available today. For example, a certain amount of current is needed in order to operate correctly. Others are more vendor specific flavors and may have unique electrical characteristics all. Design of a highspeed transistor for the aslt current switch pdf. Tis goal is to help designers easily find the ideal logic technology or function they need. The ecl basic circuits include the ornor gate, andnand gate, the reference voltage network, and ecl. Emittercoupled logic ecl is a bjtbased logic family which is. 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.
In ecl logic family, logic 0 is represented as about 1. Logic gates in the same logic family snap together like legos in. The design of the digital ics takes place by making use of bipolar devices or mos or both. The ecl families the ecl emitter coupled logic families, originated in the late 1950s and remain the fastest chips available, but consume more power, and because they use a negative power supply of 5. The skew introduced by a logic device can be broken up into three areas. Feb 23, 2015 emittercoupled logic ecl based on bipolar transistors, but removes problems of storage time by preventing the transistors from saturating very fast operation propagation delays of 1ns or less high power consumption, perhaps 60 mwgate low noise immunity of about 0. Some are defined by industry standard committees, such as the tia, ieee, or jedec groups. For the love of physics walter lewin may 16, 2011 duration.
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