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. 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. From switches to transistors, logic gates and logic circuits hakim weatherspoon cs 3410, spring 20 computer science cornell university. 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. Digital circuits also introduce the concept of two inputs creating a high output when both are high and variations of this. Transistors and logic gates uwmadison computer sciences. The concept of memory is then introduced through the construction of an sr latch and then a d flipflop. Here is a schematic diagram for an inverter gate constructed from bipolar transistors transistortotransistorlogic, also known as ttl, shown connected to a spdt switch and an led. A clock is created to be used in a basic state machine design that aims to combine logic circuits with memory.
Cmos technology and logic gates mit opencourseware. Even more serious is the voltage degradation for the cascaded andor function. Use of transistors q4 and diode is to provide quick charging and discharging of parasitic capacitance across q3. Cmosbased carbon nanotube passtransistor logic integrated. Ic logic gates fall under ssi, combinational logic circuits fall under msi, and. This is the basis for the operation for your computer and any. Following our study of amplifiers, we turn to the use of the as a. Low level state when lower transistor is on and upper transistor is off. Diodetransistor logic dtl diodetransistor logic, or dtl, refers to the technology for designing and fabricating digital circuits wherein logic gates employ both diodes and transistors. Domino logic is attractive for highspeed circuits 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. Diode transistor logic 2 and gate and logic 1 drops for the or gate. We demonstrate logic circuits with fieldeffect transistors based on single carbon nanotubes. Single transistor switches are useful as a way to a interface relatively lowpower opamp comparator output to a highcurrent or high voltage device.
Rtl is the earliest class of transistorized digital logic circuit used. Free transistor circuits books download ebooks online. Experiment 6 transistors as amplifiers and switches. Introduction to digital logic with laboratory exercises. Oct 05, 2017 ttl transistor transistor logic circuit learn and grow. In this ic circuits ebook, we made about 100 interesting circuits using integrated circuits. Digital logic circuits school of electrical engineering and. Understanding transistor circuit design electronics notes. Standard ttl transistor transistor logic 74 series the standard ttl short for transistor transistor logic logic gate was first marketed in 1963 under part numbers 74xxx. Zion asymmetrical ttl outputs i oh max i ih max 20uamps i oh max 400 uamps fanout high 400uamp 20 uamp 20 high output i oh max.
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. Rtl circuits were first constructed with discrete components, but in 1961 it became the first digital logic family to be produced as a monolithic integrated circuit. The flipflop composed of the two transistors is held in this stable state by feedback resistors r1 and r2. Recently reported logic style comparisons based on fulladder circuits claimed complementary pass transistor logic cpl to be much more powerefficient than complementary cmos. From transistorsto logic gates and logic circuits prof. However, new comparisons performed on more efficient cmos circuit realizations and a wider range of different logic cells, as well as the use of realistic. This notation of ttl or cmos refers to the logic technology used to manufacture. In most cases, the ic will contain 10 100 transistors, at a lower cost than individual components and occupies much less space. Dynamic combinational circuits dynamic circuits charge sharing, charge redistribution. Combinational logic circuit output depends only on the current inputs stateless sequential logic circuit output depends on the sequence of inputs past and present stores information state from past inputs well first look at some useful combinational circuits, then show how to use sequential circuits to store. From switches to transistors, logic gates and logic circuits hakim weatherspoon cs 3410, spring 20 computer science cornell university see.
In part i the circuits you studied were built up from combinations of simple npn transistors. Integrated circuits started with a few transistors in each chip and increased to whole mini or micro computers in a single chip. However, during turn off, q1 functions as a transistor thereby reducing the storage charge as will be obvious below. Standard commercially available digital logic gates are available in two basic families or forms, ttl which stands for transistor transistor logic such as the 7400 series, and cmos which stands for complementary metaloxidesilicon which is the 4000 series of chips. Logic circuits with carbon nanotube transistors science. Transistors and logic circuits transistor control voltage in voltage out control high allows current to flow switch is closed on control low stops current flow switch is open off 2 not gate one transistor in out in high, switch is closed so current flows to ground out is low.
The standard ttl short for transistor transistor logic logic gate was first marketed in 1963 under part numbers 74xxx. Most of your work in part ii will be using integrated circuits chips from the family of transistortransistorlogic ttl components. Transistor q1 thus acts as a backtoback diode rather than as a transistor. Diode transistor logic, or dtl, refers to the technology for designing and fabricating digital circuits wherein logic gates employ both diodes and transistors.
Free transistor circuits books download ebooks online textbooks. Drl, diodetransistor logic dtl and transistortransistor logic ttl as. Diodetransistor logic 2 and gate and logic 1 drops for the or gate. The current drive of the transistor gatetosource voltage is reduce significantly as v.
A pmos transistor acts as an inverse switch that is on when the controlling signal is low and off when the controlling signal is high. Jun 17, 2018 in this ic circuits ebook, we made about 100 interesting circuits using integrated circuits. Actually, there are many different ttl families, with a range of speed, power consumption, and other characteristics. Pdf a hybrid nanomemristortransistor logic circuit capable of self. The circuit examples in this section are based on a representative ttl family, lowpower schottky ls or lsttl. Ic positive nor gate using resistance transistor logic.
Ttl input or output lead is defined to be positive if the. Transistor transistor logic gate electronics tutorials. Combinational and sequential logic circuits hardware. Ttl transistortransistor logic families history and. James morizio 19 domino logic m p m e v dd pdn in 1 in 2 in3 out1 mp m e vdd in 4 pdn out2 m r vdd. However, new comparisons performed on more efficient cmos circuit realizations and a wider range of different logic cells, as well as the use of realistic circuit arrangements demonstrate cmos to be superior. Resistortransistor logic rtl sometimes also transistorresistor logic trl is a class of digital circuits built using resistors as the input network and bipolar junction transistors bjts as switching devices. An nmos switch is on when the controlling signal is high and is off when the controlling signal is low. Ttl transistor transistor logic circuit learn and grow. Resistor is used to keep the output current to a safe value.
Logic gates in cmos indepth discussion of logic families in cmosstatic and dynamic, pass transistor, nonran tioed and ratioed logic n optimizing a logic gate for area, speed, energy, or robustness lowpower and highperformance circuit design techniques 6. Here is a schematic diagram for an inverter gate constructed from bipolar transistors transistor to transistor logic, also known as ttl, shown connected to a spdt switch and an led. The leftmost transistor in this schematic is actually. Transistortransistor logic ttl is a class of digital circuits built from bipolar junction transistors bjt and resistors. Use switch behavior of mos transistors to implement logical functions. 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. Logic operation is same as the open collector output. An or gate immediately followed by a not gate constitutes the ornot or nor gate. The humble transistor q1 emitter e collector c base b transistor basics emitter to base junction is forward biased normally collector to base junction is reverse biased normally transistors are current operated devices, so. Integrated circuits ics are chips, pieces of semiconductor material, that contain all of the transistors, resistors, and capacitors necessary to create a digital circuit. Transistors and logic circuits transistor control voltage in voltage out control high allows current to flow switch is closed on control low stops current flow. Logic gates in cmos indepth discussion of logic families in cmosstatic and dynamic, passtransistor, nonran tioed and ratioed logic n optimizing a logic gate for area, speed, energy, or robustness lowpower and highperformance circuitdesign techniques 6. Switchlike behavior is important, because it can give rise to logic o in a cpu, we use transistors as switches, to implement logic gates. Pseudonmos logic achieves this goal by replacing the pmos stack with a single grounded pmos transistor serving as a resistive pullup.
This is called logic and introduces terms such as boolean algebra and gates. V s will initially charge up quickly, but the tail end of the transient is slow. Lecture 8 qualitative discussion on ttl circuits duration. Integrated logic circuits using singleatom transistors article pdf available in proceedings of the national academy of sciences 10834. Simple digital logic gates can be made by combining transistors, diodes and. Pass transistor logic all lecture notes are adapted from mary jane irwin, penn state, which were adapted from rabaeys digital integrated circuits, 2002, j. Transistor basics emitter to base junction is forward biased normally collector to base junction is reverse biased normally transistors are current operated devices, so kcl should be applied first. Nearly all transistors in digital cmos circuits have minimum l. Transistor transistor logic ttl is a class of integrated circuits which maintain logic states and achieve switching with the help of bipolar transistors. Also, it must be weaker than the nmos, so the rise time. The transistor on whose base the higher voltage appeared conducts, while the othe r transistor remains turned off. Only a limited number of series cascaded circuits can be used before the logic levels must be restored to the rails.
It is called transistortransistor logic because both the logic gating function and the amplifying function are performed by transistors. Figure 3 gives the circuit of a 3input positive nor gate using resistance transistor logic rtl with fan out of 5. The current coming out the output terminal is io is the sum of the currents coming down through the base and the collector. If any of the three inputs is high, corresponding transistor is driven into saturation resulting in low output. Dtl offers better noise margins and greater fanouts than rtl, but suffers from low speed, especially in comparison to ttl. Apr 25, 2012 in this electronics 201 lecture, we look at how to construct any logic gate imaginable from simple npn transistors using not logic. Figure 3a gives the circuit symbol and boolean expression for nor gate while figure 1b gives the twoinput truth table. The simplest type of digital logic circuit is an inverter, also called an inverting buffer, or not gate.
These switches are also very useful to the output of an op. Transistortransistorlogic topics the most commonly used bipolar logic family is transistor transistor logic. Our device layout features local gates that provide excellent capacitive coupling between the gate and nanotube, enabling strong electrostatic doping of the nanotube from p doping to n doping and the study of the nonconventional longrange screening of charge along the onedimensional nanotubes. A popular and widely used alternative to the conventional cmos logic configuration is the ptl configuration, which can significantly reduce the number of transistors. Its name signifies that transistors perform both the logic function the first transistor and the amplifying function the second transistor. Transistortransistor logic ttl is a logic family built from bipolar junction transistors. Transistortransistorlogic topics the most commonly used bipolar logic family is transistortransistor logic. The bipolar transistor has been available for over seventy years its technology is very well established, and although field effect transistor technology is probably more widely used in integrated circuits, bipolar transistors are still used in huge quantities in various analogue and digital circuits, both within integrated circuits and as discrete electronic components. Most of your work in part ii will be using integrated circuits chips from the family of transistor transistor logic ttl components.
Single transistor switches are useful as a way to a interface. Transistor transistor logic topics the most commonly used bipolar logic family is transistor transistor logic. In this electronics 201 lecture, we look at how to construct any logic gate imaginable from simple npn transistors using not logic. Discrete transistor circuits 197 audio circuits 202 simple active.
989 1239 1440 609 931 27 874 538 1230 251 1496 699 1456 1477 642 97 439 1232 994 1026 1152 882 91 1397 1175 1014 242 16 710 937 1322 1166 888 993 22 1043 1125 857 640 1077 20 946 93