Transistortransistor logic or ttl is a family of logic circuits used in electronics invented in the 1960s. Transistor transistor logic is a logic family built from bipolar junction transistors. Transistor characteristics are the plots which represent the relationships between the current and the voltages of a transistor in a particular configuration. Transistor transistor logic ttl is a class of integrated circuits which maintain logic states and achieve switching with the help of bipolar transistors. The fundamental operation of pnps is the same as that of npns, but the polarities are reversed in a way that sometimes leads to awkward circuit configurations. Ttl1 time to live a counter in a network packet that sets a limit to its validity.
The input to a ttl circuit is always through the emitters of the input transistor, which exhibits a. Transistortransistor logic ttl transistortransistor logic, or ttl, refers to the technology for designing and fabricating digital integrated circuits that employ logic gates consisting primarily of bipolar transistors. A particular characteristic of ttl signals is that the inputs to a gate float high i. Ttl, or transistortransistor logic, is a digital circuit that uses multiple transistors to derive its output. Transistor transistor logic watch more videos at videotutorialsindex. Unfortunately, dctl has much smaller signal levels, has more. The word transistor is a combination of the two words trans fer var istor which describes their mode of operation way back in their early days of electronics development. For example, the diode d2 from figure 2 in the chapter on dtl can be replaced by a transistor whose collector is pulled up to the power supply. The circuit examples in this section are based on a representative ttl family, lowpower schottky ls or lsttl.
Transistor logic switches, also known as transistortransistor logic ttl became widespread after the invention of the bipolar junction transistor bjt. One of the prominent features of transistor transistor logic signals is the ability of the inputs of the gate rise to the logical 1 if left unconnected. Transistortransistor logic ttl is a logic family built from bipolar junction transistors. Disclosed is a transistortransistorlogic ttl circuit which is testable by d. We will try to keep the article as brief and easy as possible. It has been described as the workhorse of the electronics industry and the base technology of the late 20th to early 21st centuries. Transistor q1 thus acts as a backtoback diode rather than as a transistor. Transistortransistor logic ttl is a class of integrated circuits which maintain logic states and achieve switching with the help of bipolar transistors. Transistor logic and then transistor transistor logic, dtl and ttl respectively. Jun 02, 2017 transfer characteristics are plots which are drawn between current and voltages of transistor in given configuration a transistor can be analyzed by characteristics curve which are as follows 1. The first family of transistors, sylvania universal highlevel logic suhl, was produced.
Transistortransistor logic ttl is a digital logic design in which bipolar transistor s act on directcurrent pulses. Over previous technologies, ttl had speed and reliability. In transistor transistor logic, transistors can both amplify the output and isolate the inputs. Jan 26, 2018 for the love of physics walter lewin may 16, 2011 duration. The current coming out the output terminal is io is the sum of the currents coming down through the base and the collector. This is a logic family which is mainly build up of npn transistors, pn junction diodes and diffused resistor s. Transistor transistor logic ttl family one basic function of ttl ic is as a complimenting switch or inverter. Transistor switches are used for a wide variety of applications such as interfacing large current or high voltage devices like motors, relays or lamps to low voltage digital ics or logic gates like and gates or or gates. Ttl transistor transistor logic circuit digital logic. The full form of ttl is transistor transistor logic. Transistortransistor logic ttl a common semiconductor technology for building discrete digital logic integrated circuits. Its name signifies that transistors perform both the logic function the first transistor and the amplifying function the second transistor. What are the characteristics of diode transistor logic answers. The above figure shows the internal structure and characteristics.
The insulatedgate bipolar transistor igbt is a power transistor with characteristics of both a mosfet and bipolar junction transistor bjt. An or gate immediately followed by a not gate constitutes the ornot or nor gate. Transistortransistor logic ttl is a class of digital circuits built from bipolar junction transistors bjt and resistors. Sep 29, 2018 its name signifies that transistors perform both the logic function the first transistor and the amplifying function the second transistor. Current flows out of the collector, and the collector. Disclosed is a transistor transistor logic ttl circuit which is testable by d.
Rtl gates are now seldom used, if at all, in modern digital electronics design because it has several drawbacks, such as bulkiness, low speed, limited fanout, and poor. Transistor transistor logic or ttl electrical study app. There are two basic types of bipolar transistor construction, pnp and npn, which basically describes the physical arrangement of the ptype and ntype semiconductor materials from which they are. What are the basic differences between cmos and ttl signals. Transfer characterstics of transistortransistor logic family. The invention of the semiconductor transistor in 1947 at bell laboratories 11 and the improvements in transistor characteristics and fabrication during the 1950s led to the introduction of linear analogue ics and the first transistortransistor logic ttl digital logic ic in the early 1960s, closely followed by complementary metal oxide.
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. Rtl gates are now seldom used, if at all, in modern digital electronics design because it has several drawbacks, such as. So logic was done with basic common emitter or common collector config. The high impedance network can be a schottky barrier diode and an epitaxial. Ttl is a digital logic design where transistors act on dc pulses. Resistortransistor logic rtl resistortransistor logic, or rtl, refers to the obsolete technology for designing and fabricating digital circuits that employ logic gates consisting of nothing but transistors and resistors. Transistors are basically fancyspeak for electrically controlled switches. Propagation delays are 10 ns when driving a 15 pf400 ohm load. The standard ttl short for transistor transistor logic logic gate was first marketed in 1963 under part numbers 74xxx. The list of acronyms and abbreviations related to ttl transistortransistor logic. Transistor transistor logic gate electronics tutorials.
A transistor is a linear semiconductor device that can control a larger current through one of its terminals with a low power applied electrical signal, which could be either a current, as in the case of a bipolar junction transistor bjt, or a voltage, when it is called a fieldeffect transistor. In electronics, emittercoupled logic ecl is a highspeed integrated circuit bipolar transistor logic family. Transistor transistor logic ttl is a series of integrated logic chips that accept external digital inputs through a multiemitter transistor and than produce a digital output using another transistor, and also uses transistors to reproduce and interconnect the required logic functions. Ttl is bipolar logic, meaning it contains at least one bjt, or a bipolar junction transistor, which contributes to the amplifying power of transistor transistor logic. In order to prevent an ip packet from propagating endlessly through the network, the value in the ttl field is reduced by each router. Diodetransistor logic dtl was used in the ibm 608 which was the first alltransistorized computer.
What is the summary of the poem kitchen by taufiq rafat. However, during turn off, q1 functions as a transistor thereby reducing the storage charge as will be obvious below. A particular characteristic of ttl signals is that. All these emittercollector junctions currentstable elements are connected in parallel. Every emittercollector junction every ttl input acts as a transistor current sink pulling a small current about 40. We shall begin this section with a study of the evolution of ttl from dtl. Transfer characterstics of transistortransistor logic. The transistor actively pulls the output down to logic 0, but the resistor is not active in pulling the output up to logic 1. What are the characteristics of diode transistor logic. Consequently, dctl gates have fewer components, are more economical, and are simpler to fabricate onto integrated circuits than rtl gates.
The purpose of this experiment is to provide an understanding of some of the characteristics of the transistor transistor logic ttl family and complementary. It overcomes the main problem associated with dtl, i. The basic building block of this logic family is nand gate and there are various subfamilies of this logic gate those are standard ttl, advanced schottky ttl, schottky ttl, low power ttl, high power ttl, fast ttl etc. With any of the input at logic low, the corresponding emitterbase junction is forward biased and the voltage drop across the base of q1 is around 0. Individual transistors still cost money in the 1960s. Ttl transistortransistor logic families history and. Transistor transistor logic 1 chapter 6 transistor transistor logic the evolution from dtl to ttl can be seen by observing the placement of pn junctions.
Any twoport network which is analogous to transistor configuration circuits can be analysed using three types of characteristic curves. Transistortransistorlogic topics the most commonly used bipolar logic family is transistortransistor logic. Rtlresistor transistor logic dtl diode transistor logic ttltransistortransistor logic eclemitter coupled logic cmoscomplementary metal oxide semiconductor logic. The most commonly used bipolar logic family is transistortransistor logic. Transistortransistor logic university of st andrews. Transistor transistor logic transistor transistor logic the most commonly used bipolar logic family, there are many different ttl families, with a range of speed, power consumption, and other characteristics. Ttl family the logic family refers to the general physical realization of a logical element, such as the ttl, emittercoupled logic ecl, or complementary metaloxide semiconductor cmos logic families. The purpose of this experiment is to provide an understanding of some of the characteristics of the transistortransistor logic ttl family and complementary.
Many ttl logic gate s are typically fabricated onto a single integrated circuit ic. Directcoupled transistor logic dctl is similar to resistor transistor logic rtl but the input transistor bases are connected directly to the collector outputs without any base resistors. As the current is steered between two legs of an emittercoupled pair, ecl is sometimes called. It is the most common transistor in electronics, and the most widely used semiconductor device in the world. Transistor q1 behaves as a cluster of diodes placed back to back. Transistortransistor logic article about transistor. Transistortransistor logic ttl is a class of integrated circuits which maintain logic states and achieve switching with the help of bipolar. Ttl transistortransistor logic families history and applications.
Ttl integrated circuits were widely used in applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, and synthesizers. Transistor logic and then transistortransistor logic, dtl and ttl respectively. Indeed, the bulk of digital systems applications employing ssi and msi packages were designed using ttl. May 30, 2019 transistor characteristics are the plots which represent the relationships between the current and the voltages of a transistor in a particular configuration. Transfer characteristics are plots which are drawn between current and voltages of transistor in given configuration a transistor can be analyzed by characteristics curve which are as follows 1.
Figure 3a gives the circuit symbol and boolean expression for nor gate while figure 1b gives the twoinput truth table. Early transistorized computers were implemented using discrete transistors, resistors, diodes and capacitors. Some ttl logic gates are fabricated onto an integrated circuit ic. Transistor characteristics in physics, the graph representing the relationships between the current and the voltage of any transistor of any configuration is called transistor characteristics. Due to inevitable factors such as circuit capacitances and a characteristic of bipolar transistors called charge storage, it will take a certain amount of time for the transistor to turn completely off and the output. A from the upper transistor v3 of the previous stage. Sep 14, 2016 this version of ttl circuit is not available now. By considering the transistor configuration circuits to be analogous to twoport networks, they can be analyzed using the characteristiccurves which can be of the following types. Ttl electronics transistortransistor logic ttl 1 transistortransistor logic. Actually, there are many different ttl families, with a range of speed, power consumption, and other characteristics. It is called transistortransistor logic because both the logic gating function and the amplifying function are performed by transistors. Dtl was initially made with discrete transistors and resistors before being integrated onto silicon. Unlike the low power ttl the high power ttl is the high speed edition.
A logic family is the type of components used to make logic gates on an ic. Transistor transistor logic or ttl electrical study app by. What are the advantages of ttl transistor transistor logic. It relies on circuits built from bipolar transistors to achieve switching and maintain logic states. The first diodetransistor logic family of integrated circuits was introduced by. Transistor transistor logic article about transistor. The standard ttl short for transistor transistor logic logic gate was first. The mosfet forms the basis of modern electronics, and is the basic element in most modern electronic equipment. The most commonly used bipolar logic family, there are many different ttl families, with a range of speed, power consumption, and other characteristics. One of the prominent features of transistortransistor logic signals is the ability of the inputs of the gate rise to the logical 1 if left unconnected. Mar 15, 2020 the full form of ttl is transistor transistor logic. For the love of physics walter lewin may 16, 2011 duration. Transistor and diode chips were glued to a ceramic substrate. One early form of dtl, used by ibm corp in the 360 family of computers, was really a hybrid technology.
A switching transistor could perform the logic function and the amplifying function, which changed the digital electronics industry overnight. Jun 15, 2018 transistor transistor logic or ttl is a family of logic circuits used in electronics invented in the 1960s. Ttltransistortransistor logic, a logic family to realize logic gates, can be open collector, totem pole or tri state. 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. The improvement includes a high impedance network for providing sufficient base drive to drive the output transistor into conduction when the malfunctioning input transistor fails to provide a turnoff logic level. Its name signifies that transistors perform both the logic function and the amplifying function. Its name signifies that transistors perform both the logic function the first.