Ttl and cmos logic and their characteristics pdf

For example, the diode in the dtl can be replaced by a transistor whose collector is pulled up to the power supply. Introduction and comparison of 74hct ttl compatible cmos logic. Texas instruments ti reserves the right to make changes to its products or to discontinue. Todays computer memories, cpus and cell phones make use of this technology due to several key advantages. The ttl family the input of a ttl logic gate is characterized by a multi emitter transistor.

Little logic devices in 5pin sot23, 5pin sc70, 6pin sot23, 6pin sc70, 8pin sm8, 8pin us8 and the. Rtlresistor transistor logic dtldiode transistor logic ttltransistortransistor logic eclemitter coupled logic cmos complementary metal oxide semiconductor logic out of these rtl and dtl are rarely used. Difference between cmos and ttl compare the difference. Complete the table below by writing the expanded names of the three most popular logic families. Its name signifies that transistors perform both the logic function the first transistor and the amplifying function the second transistor.

Logic gates are classified not only by their logical functions, but also by their logical families. The output stage of most ttl logic is a totempole circuit. Cmos vs ttl ttl stands for transistortransistor logic. Cmos technology and logic gates mit opencourseware. Characteristics of logic families are speed, fanin, fanout, noise immunity, power dissipation.

Even with the specified incompatibility, it is possible to improve the ttl cmos interface without using hct. Ttl transistortransistor logic families history and. Because digital circuits have no linear input and output characteristics, the. Cmos logic families first commercially available cmos family was the 4000 series. This time the admin will explain the types of logic gate ic along with the schematics that can be used for practice. Transistors are basically fancyspeak for electrically controlled switches. The circuit examples in this section are based on a representative ttl family, lowpower schottky ls or ls ttl. In other words, cmos circuits can tolerate over twice the amount of superimposed noise voltage on their input lines before signal. Consult one or more ic datasheets for legacy ttl logic circuits not the newer highspeed cmos 54hcxx and 74hcxx chips to obtain your answer. In computer engineering, a logic family may refer to one of two related concepts. Several new cmos families were introduced in the 1980s and the 1990s. For practice or experiment using logic gate you can use logic gate made of switch, diode, relay and so on. Ttlcmos interface with opencollector output and pullup resistor. The name is derived from the use of two bipolar junction transistors or bjts in the design of each logic gate.

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. In typical cmos logic ics v cc 5 v, the lowlevel input voltage v ilmax is 1. Zion fanout the fanout of a logic gate is the number of inputs that the gate can drive without exceeding its worstcase loading specifications. Many logic families were produced as individual components, each. Sep 29, 2012 the set of logic gates constructed using coupled transistors and resistors are collectively known as ttl gate family. It should be obvious from these figures that cmos gate circuits have far greater noise margins than ttl.

Transistortransistor logic ttl is a logic family built from bipolar junction transistors. For proper operation the input voltage levels to a logic must be kept. Introduction and comparison of 74hct ttl compatible cmos. Determine ic input and output voltage and current ratings from the manufacturers data manual. Difference between ttl and cmos ics and how to choose. Uses both nmos and pmos transistors in complementary fashion. Transistor transistor logic ttl 1 transistor transistor logic ttl ttl basics of operation. Logic signal voltage levels logic gates electronics. Analyze internal circuitry of a ttl nand gate for both high and low output states. Fanout must be examined for both possible output states.

Types of logic families in digital electronics are ttl, cmos complementary metaloxide semiconductor, ecl, rtl, dtl. For this reason, only the most important circuits and their behavior are discussed. Ttl stands for transistortransistor logic, this logic family having replaced the. Cmos technology is one of the most popular technology in the computer chip design industry and broadly used today to form integrated circuits in numerous and varied applications. As well as ttl and cmos technology, simple digital logic gates can also be made by connecting together diodes, transistors and resistors to produce rtl, resistortransistor logic. Cmos vlsi is thedigital implementation technology of choice for the foreseeable future next 1020 years excellent energy versus delay characteristics high density of wires and transistors monolithic manufacturing of devices and interconnect, cheap. All logic gates exhibit a propagation delay when responding to changes in their inputs the most widely used logic families are cmos and ttl cmos is available in a range of forms offering high speed or very low power consumption ttl logic is also produced in many versions, each optimised for. The set of logic gates constructed using coupled transistors and resistors are collectively known as ttl gate family. Actually, there are many different ttl families, with a range of speed, power consumption, and other characteristics. Although the operation speed of cmos logic in the early days was slower than that of ttl, cmos logic, employing fine processes, now achieves higher speed than that of ttl. Transistortransistorlogic topics the most commonly used bipolar logic family is transistortransistor logic. Characteristics of logic families in digital electronics. However, the following comments apply to all other bipolar logic families.

With hc and hct logic and ls ttl logic competing in the market it became clear famjlies further improvements were needed to create the ideal logic device that combined high speed, with low power dissipation and. The trio received a nobel prize in physics for their. In this particular case, the way the load led is connected to the output of the gate, the gate will only source current. Q2 is in cutoff since it gets no base current from q1. 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. Within each family, several subfamilies of logic types are. The circuit examples in this section are based on a representative ttl family, lowpower schottky ls or lsttl. Little logic devices from texas instruments ti are the pieces that help complete the design puzzle. Low power schottky lsttl was the industry standard logic family for many years. However, the gate is capable of sinking current from a load, if. Supplanted ttl, thanks to its superior speed and low power consumption. Interfacing ls ttl outputs to standard cmos inputs using a pullup resistor.

Digital logic circuits are manufactured depending on the specific circuit technology or logic families. Logic families and their characteristics 1 chapter 9. Ttl logic family the evolution from diode transistor logic to transistor transistor logic can be seen by observing the placement of pn junctions. The adg633 is available in a small, 16lead tssop package and a 16lead, 4 mm. Although the 4000series offered low power consumption, they were slow and difficult to interface with the more popular at the time bipolar ttl family. Logic families and their characteristics website staff ui.

We will model this behavior using switches controlled by voltages corresponding to logic 0 and logic 1. As t3 saturates, its collector voltage will fall to about 0. Generally speaking, ttl logic ics use npn and pnp type bipolar junction transistors while cmos logic ics use complementary mosfet or jfet type field effect transistors for both their input and output circuitry. Oct 26, 2019 digital ic gates are classified not only by their logic operation, but also by the specific logic circuit family to which it belongs. Cmos technology working principle and its applications. Cmoslogic digital logic families electronics tutorial. Sep 29, 2018 11 videos play all digital logic families by dinesh arya tech gurukul characteristics of logic families duration.

Transistortransistor logic university of st andrews. These families are about twice as fast as hchct while maintaining backwards compatibility with their predecessors. What are the basic differences between cmos and ttl signals. Even low voltage swing ttl devices such as the fct family have ttl high output voltages above 4. Ttl input or output lead is defined to be positive if the. Ttl gates equipped with totempole output circuitry are able to both source and sink load current. When using ics of one logic family exclusively, you need not be. Although there are many ways of making integrated circuits, and several technologies. However, the gate is capable of sinking current from a load, if only the load were connected differently. 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. Cmos is better for general use because it draws no current unless switching, and. Request pdf ttl logic and cmosttl interface this chapter starts with transistortransistorlogic ttl, explains the circuit operation of a ttl inverter, ttl nand and nor gates, their logic. Ttl and cmos are two of the most common logic families. Very fast bipolar logic but consumes too much power and hence not used.

Cmos gate is the sum of gate capacitance diffusion capacitance routing capacitance understanding the source of parasitic loads and their variations is essential in the design process. Figure1 depicts ttl to cmos interfacing and cmos to ttl interfacing circuits. In fact logic gates can be implemented in pneumatic and hydraulic systems for special purpose applications in hazardous areas in petrochemical plants. The popularity of these ttl families stem from their ease of use, low cost, mediumtohigh speed operation, and good output drive capability.

A 5v cmos driver will drive the bus to 5v at a logic high. Texas instruments ti reserves the right to make changes to its products or to discontinue any. Interfacing lsttl outputs to standard cmos inputs using a pullup resistor. For input low, current ir flows out the input e of q1 into the output of inverter driving input. Voltage levels range from 0 to vcc where vcc is typically 4. The term cmos stands for complementary metal oxide semiconductor. 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. A two input gate will have two emitters and a four input gate will have four emitters. Some of the main ttl and cmos subfamilies currently in use are compared in fig. Within each family, several subfamilies of logic types are available, with different rating for speed, power consumption. The logic levels for cmos differ markedly from those associated with ttl. The input of a ttl logic gate is characterized by a multi emitter transistor.

Four major logic families that predominated from the 1970s through the 1990s are transistortransistor logic ttl, complementary metaloxidesemiconductor logic cmos, pronounced seamoss, low voltage ttl logic lvttl, and low voltage cmos logic lvcmos. Transistortransistor logic topics the most commonly used bipolar logic family is transistortransistor logic. Ttl logic family digital logic families electronics. Ttl and cmos characteristics purpose logic gates are classified not only by their logical functions, but also by their logical families. Figure 1 shows the simplified circuit of a ttl device with diode inputs, such as are used with devices in the sn74ls. It relies on circuits built from bipolar transistors to achieve switching and maintain logic states. Emitter coupled logic ecl or current mode logic cml 6. This is a popular logic family which includes 4000a, 4000b, 4000ub, 5474c, 5474hc, 5474hct, 5474ac and 5474act families. Propagation delays are 10 ns when driving a 15 pf400 ohm load. Ppt logic families and their characteristics powerpoint.

A particular characteristic of ttl signals is that. All logic gates exhibit a propagation delay when responding to changes in their inputs the most widely used logic families are cmos and ttl cmos is available in a range of forms offering high speed or very low power consumption ttl logic is also produced in many versions, each optimised for a particular characteristic. On this channel you can get education and knowledge for general issues and topics. Their extremely small size gives designers the ability to greatly simplify design routing and maximize asic design development.

Wh l i ttl nand i l h when at least one input to a ttl nand gate is low, the. For this course, we need to study only ttl and cmos mostly ttl. Dec 30, 2018 the ics which belong to ttl family are designated as follows 74 or 54 for standard ttl, 74l or 54l for lowpower ttl, 74h or 54h for high power ttl, 74ls or 54ls for low power schottky ttl and so on. Logic families significance and types of logic families. The two differ in the characteristics of the semiconductor materials used in their implementation and in the mechanism governing the conduction of a current through them. Cmos logic cmos logic ics consume less power than ttls. Application note 3 dc electrical characteristics of mm74hc high. Chapter 4 electrical characteristics of cmos jinfu li department of electrical engineering national central university. An11a q bus switches provide 5v and 3v logic quality. 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. What are the basic differences between cmos and ttl. This allows the lt1016 to remain stable with the outputs in the active region which, greatly reduces the problem of output glitching when the input signal is slow moving or is low level.

Dec 29, 2019 logic families are defined as a group of electronic logic gates and circuits used in ic integrated circuits. The 3v lvttl devices cannot withstand more than approximately 3. Even with the specified incompatibility, it is possible to improve the ttlcmos interface without using hct. There are many fabrication techniques used in ic manufacturing the two most popular types are the transistor transistor logic ttl which got.