Physics
Digital Circuits
Digital circuits are electronic circuits that operate using digital signals, which are discrete voltage levels representing binary values. They are composed of components such as logic gates, flip-flops, and multiplexers, and are the building blocks of digital systems like computers and microcontrollers. Digital circuits process and manipulate digital information, making them essential in modern technology and electronics.
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12 Key excerpts on "Digital Circuits"
eBook - PDFDigital Electronic Circuits
Principles and Practices
- Shuqin Lou, Chunling Yang(Authors)
- 2019(Publication Date)
- De Gruyter(Publisher)
1 Introduction to digital electronic circuit 1.1 Introduction Electronics is a branch of physics, engineering, and technology that deals with circuits consisting of components that control the flow of electricity. Circuits and components can be divided into two groups: analog and digital. A particular device may consist of circuitry that has analog or digital or a combination of these. Digital electronics or digital electronic circuits operate on digital signals. In the early days, applications of digital electronic circuits were focused on computer systems. Now digital electronics has been applied in a wide range of systems, such as telecommu-nication systems, military systems, medical systems, control systems, and consumer electronics. This chapter provides a broad overview of digital electronic circuits, including a brief introduction to the basic concepts of Digital Circuits, their commonly used devices, and technology of electronic design automation (EDA). The objectives of this chapter are to – Explain the differences between digital and analog quantities – Describe the representation of digital quantities – Explain the classification of Digital Circuits – State the advantages of digital over analog – Explain the characteristics of the commonly used hardware description lan-guages (HDLs) – Define EDA – Describe the design and programming process of programmable logic device (PLD) 1.2 Introductory basic concepts of digital electronic circuit Electronic systems can be divided into two broad categories: digital and analog. Digital Circuits are electric circuits that deal with the digital signals that have a number of discrete voltage levels. To most engineers, the terms “ digital circuit, ” “ digital system, ” and “ logic ” are interchangeable in the context of Digital Circuits, while analog circuits involve quantities with continuous values. This section intro-duces some basic concepts about Digital Circuits.
eBook - ePubElectronics Explained
The New Systems Approach to Learning Electronics
- Louis E. Frenzel(Author)
- 2010(Publication Date)
- Newnes(Publisher)
Electronic Circuits: Digital
Practically Everything Is Digital These DaysIn this Chapter:INTRODUCTIONBinary number system.Logic gates and flip-flops.Common combinational and sequential circuits.Semiconductor memory.Programmable logic devices.Analog-to-digital and digital-to-analog conversion.Recall that there are two basic types of electronic signals—analog and digital. A digital signal is one that varies in discrete steps. Unlike an analog signal, which varies continuously, a digital signal has two levels or states. The signal switches or changes abruptly from one state to the other.Figure 5.1 shows a DC digital signal that switches between two known levels such as zero volts or close to it (<0.1 volt) or 0 V and +3.3 V. The positive voltage can be anything between about 1 volt and 12 volts with 3.3 and 5 being the most common.Digital signals with two discrete levels are also referred to as binary signals. Binary means two—two states or two discrete levels of voltage.Humans use the decimal number system that represents quantities with digits 0 through 9. However, digital equipment and computers do not. Internally, digital equipment processes binary data.FIGURE 5.1 Binary signal that represents 0 and 1 as voltage levels.BINARY NUMBERSThe binary number system is a set of rules and procedures for representing and processing numerical quantities in digital equipment. Because the base of the binary number system is 2, only two symbols (0 and 1) are used to represent any quantity. The symbols 0 and 1 are called binary digits or bits . For example, the 6-bit number 101101 represents the decimal number 45. Your understanding of how Digital Circuits, microprocessors, and related equipment process data is tied directly to an understanding of the binary number system.The reason for using binary numbers in digital equipment is the ease with which they can be implemented. The electronic components and circuits used to represent and process binary data must be capable of assuming two discrete states to represent 0 and 1. Examples of two-state components are switches and transistors. When a switch is closed or on, it can represent a binary 1. When the switch is open or off, it can represent a binary 0. A conducting transistor may represent a 1, whereas a cut-off transistor may represent a 0. The representation may also be voltage levels. For example, a binary 1 may be represented by +3.3 V and a binary 0 by 0 V as previously shown in Figure 5.1
eBook - ePubUnderstanding Microelectronics
A Top-Down Approach
- Franco Maloberti(Author)
- 2011(Publication Date)
- Wiley(Publisher)
CHAPTER 8 DIGITAL PROCESSING CIRCUITSThis chapter introduces you to the electronic circuits for digital processing. These very complex circuits are made up of millions or even billions of transistors. The complexity involves many levels of hierarchy and requires the use of macro-functions. Often circuits are software controlled or software reconfigurable. The goal of this chapter is not to describe the circuits in detail but to help you in understanding their high-level features and in getting the flavor of typical circuit tasks – what is commonly called “hardware design.” We shall study how to interface digital blocks, how to transfer digital data and how macro-functions are implemented. Finally we shall discuss the types and features of memories.8.1 INTRODUCTIONDigital Circuits handle numbers. The word “digital” comes from “digit,” which means one of a set of symbols representing integers or real numbers. The Latin word digita (which refers to the fingers of the two hands) corresponds to 10, the basis of the 10−number decimal system. However, although the word “digital” therefore implies 10 symbols, the numerical calculation performed by Digital Circuits uses two digits, one (“1”) and zero (“0”), to represent numbers using binary methods. Therefore, in electronics disciplines the word “digit” serves to distinguish not 10 but just two symbols, also called bits .The use of two symbols is required so as to distinguish between two electrical states. Typically, low voltage (or current) represents the logic zero and high voltage (or current) depicts the logic one. Low and high are obviously defined with respect to the supply interval. Moreover, the logic levels are within the supply range. If the bias of the circuit is 0−-1.8 V, logic zero is equal to or slightly above 0 V and logic one is somewhat below 1.8 V. To be more precise, we divide the supply interval into three regions: a low range, a high range, and an intermediate interval not defined by any symbol, as shown in Figure 8.1
- Andrew Singmin(Author)
- 2001(Publication Date)
- Newnes(Publisher)
Fundamentals of Analog Circuits and Introduction to Digital Circuits 17 Digital Electronics We've seen now four common examples of basic analog circuit functions. A lot of complex circuits can be broken down into these four basic building blocks, simplifying the understanding process. The analog process has been around for a long while and will continue to be there in spite of the omnipresent digital world. Because of the prevalence of computer technology, digital technology (the basis of computer technology) probably has been brought to the forefront. Digital electronics works on a basis of two discrete values, called logic states, most commonly represented by two specific voltage levels. Generally a high logic level is associated with a high voltage level, and a low logic level with a low voltage level. The logic high state is also represented by the unit 1 and the logic low state by the unit 0. By generating the appro-priate sequence of logic bits we can thus make up logic values. As there are only two logic states and hence two voltage levels, this system is known as a binary system. That makes a nice introduction into our new section on digital electronics. Digital Logic Levels All digital electronics is founded on a system of1s and Os or high and low voltages to formulate a series of words that ultimately represent an analog equivalent. Known formally as a binary coded decimal or BCD system, this system represents decimal numbers in a binary format. Table 2-1 Four-Bit BCD Coding System Decimal Binary Code Digit A B C D 0 0 0 0 0 1 0 0 0 1 2 0 0 1 0 3 0 0 1 1 4 0 1 0 0 5 0 1 0 1 6 0 1 1 0 7 0 1 1 1 8 1 0 0 0 9 1 0 0 1 10 1 0 1 0 11 1 0 1 1 12 1 1 0 0 13 1 1 0 1 14 1 1 1 0 15 1 1 1 1 18 BEGINNING DIGITAL ELECTRONICS THROUGH PROJECTS To see more closely the generation pattern for converting decimal numbers to binary, take a look at a three-bit system below.
eBook - PDF- Dale R. Patrick, Stephen W. Fardo, Vigyan Chandra(Authors)
- 2020(Publication Date)
- River Publishers(Publisher)
Chapter 1 Introduction to Digital Systems Chapter 1 provides an overview of electronic digital systems. The concepts discussed in this chapter are important for developing an under-standing of electronic digital systems. Digital electronics is undoubtedly the fastest growing area in the field of electronics today. Personal com-puters, cameras, cell phones, calculators, watches, clocks, video games, test instruments and home appliances are only a few of the applications of digital systems. Digital systems play an essential role in our daily lives and new applications are emerging at a rapid pace. DIGITAL AND ANALOG ELECTRONICS SYSTEMS Electronics is further divided into two main categories: analog and digital. Analog electronics deals with the analog systems, in which sig-nals are free to take any possible numerical value. Digital electronics deals with digital or discrete systems, which has signals that take on only a lim-ited range of values. Practical systems are often hybrids having both ana-log and discrete components. Analog as in the term ‘analogous’, is used to represent the varia-tion of an electrical quantity when a corresponding physical phenomenon varies. For example, when the flow of fluid through a pipe increases, an analog meter monitoring the flow may generate a larger voltage (or other electric quantity), which can then be displayed on a scale calibrated to indicate flow rate. Most quantities in nature are inherently analog—tem-perature, pressure, flow, light intensity change, loudness of sound, current flow in a circuit, or voltage variations. Digital signals are characterized by discrete variations or jumps in their values. They are useful in producing information about a system. For example, in the case of a sensor monitoring the flow rate in a water canal, it might be sufficient to know whether the flow has reached a critical level, rather than monitoring every possible value of the flow. All values below 1
- Dennis L. Eggleston(Author)
- 2011(Publication Date)
- Cambridge University Press(Publisher)
8 Digital Circuits and devices 8.1 Introduction In analog electronics, voltage is a continuous variable. This is useful because most physical quantities we encounter are continuous: sound levels, light intensity, temperature, pressure, etc . 1 Digital electronics, in contrast, is characterized by only two distinguishable voltages. These two states are called by various names: on/off, true/false, high/low, and 1/0. In practice, these two states are defined by the circuit voltage being above or below a certain value. For example, in TTL logic circuits, a high state corresponds to a voltage above 2.0 V, while a low state is defined as a voltage below 0.8 V. 2 The virtue of this system is illustrated in Fig. 8.1 . We plot the voltage level versus time for some electronic signal. If this was part of an analog circuit, we would say that the voltage was averaging about 3 V, but that it had, roughly, a 20% noise level, rather large for most applications and thus unacceptable. For a TTL digital circuit, however, this signal is always above 2.0 V and is thus always in the high state. There is no uncertainty about the digital state of this voltage, so the digital signal has zero noise. This is the primary advantage of digital electronics: it is relatively immune to the noise that is ubiquitous in electronic circuits. Of course, if the fluctuations in Fig. 8.1 became so large that the voltage dipped below 2.0 V, then even a digital circuit would have problems. 8.2 Binary numbers Although Digital Circuits have excellent noise immunity, they also are limited to producing only two levels. This does not appear to be very helpful in representing the continuous signals we so frequently encounter. The solution starts with the 1 This holds for most macroscopic quantities. On the atomic level, many physical quantities are quantized. 2 If the voltage is between these thresholds, we say the state is undetermined, which means the circuit behavior cannot be insured.
eBook - ePubElectronics Explained
Fundamentals for Engineers, Technicians, and Makers
- Louis E. Frenzel(Author)
- 2017(Publication Date)
- Newnes(Publisher)
Chapter 5Electronic Circuits: Digital
Practically Everything Is Digital These Days
Abstract
This chapter is devoted to Digital Circuits. It begins with an overview of the binary number system and introduces binary codes such as binary-coded decimal and American Standard Code for Information Interchange. Next comes full coverage of logic circuits such as the inverter, AND, OR, NAND, NOR, and XOR gates. Then basic combinational logic circuits are covered and include the multiplexer, decoder, comparator, and adder. Flip flops such as the latch, D-type, and JK are covered next along with their common applications. Then the discussion turns to counters, registers, and shift registers. Types of memory such as static random access memory, dynamic random access memory, and flash are explained. Then coverage turns to programmable logic types such as the field programmable gate array. The chapter ends with an explanation of analog-to-digital converters and digital-to-analog converters and their application. Projects include building and demonstrating logic circuits and a typical counter.In this ChapterKeywords
AND; Binary; Counters; Data converters; Digital; Flip flops; FPGAs; Logic gates; Memory; NAND; NOR; OR; Shift registers; XOR• Binary number system. • Logic gates and flip-flops. • Common combinational and sequential circuits. • Semiconductor memory. • Programmable logic devices. • Analog-to-digital and digital-to-analog conversion.Introduction
Recall that there are two basic types of electronic signals—analog and digital. A digital signal is one that varies in discrete steps. Unlike an analog signal, which varies continuously, a digital signal has two levels or states. The signal switches or changes abruptly from one state to the other.Fig. 5.1 shows a DC digital signal that switches between two known levels such as 0 V and close to it (0.1 V) or 0 and 3.3 V. The positive voltage can be anything between about 1 and 12 V with 3.3 and 5
eBook - PDFPrinciples of Transistor Circuits
Introduction to the Design of Amplifiers, Receivers and Digital Circuits
- S W Amos(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
C H A P T E R 15 Digital Circuits I N T R O D U C T I O N As mentioned in the previous two chapters, transistors in multi-vibrators and other pulse circuits are used as switches, i.e. except for the brief periods during which the transistors are changing state they are either on (taking considerable current) or off (non-con-ductive). For most of the time therefore the collector (or drain) voltage has one of two possible values namely a low value near emitter or source potential (when the transistor is on) and a high value near the supply potential (when the transistor is off). A vast range of circuits has been developed during the past decade or two in which diodes and transistors are used as switches and in which the signal paths have at all times one or other of two possible voltage levels. Such circuits are used to perform mathematical and logical operations on signals in computers and similar equipment. Circuits used in this manner are known as digital or logic circuits and the principal types are described briefly in this chapter. LOGIC LEVELS The two significant values of voltage on the signal-carrying lines are referred to as logic level 0 and logic level 1.* If level 1 is more positive than level 0 the circuit is said to use the positive logic convention and if level 1 is more negative than level 0 the circuit is said to use the negative logic convention. The distinction is important because circuits can behave differently according to the logic convention * The two levels could alternatively be values of current or more generally of air pressure in pneumatic systems or fluid pressure in hydraulic systems. 252 Digital Circuits 253 binary number decimal equivalent 1 1 10 2 11 3 100 4 101 5 110 6 111 7 1000 8 1001 9 chosen. This is illustrated below but it is worth stressing now that the logic convention chosen should always be stated or implicit on diagrams of logic circuits.
eBook - PDF- Edward Keonjian(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
PHYSICAL R E A L I Z A T I O N OF D I G I T A L L O G I C C I R C U I T S A R T H U R W . L O Princeton University, Princeton, N.J., and International Business Machines Corporation, Poughkeepsie, New York 1. I N T R O D U C T I O N M I C R O P O W E R operation is imperative for digital information processing systems where circuit elements (ranging from 1 0 3 to 10 5 in number) have to operate within a restricted temperature range in high density packages and with strictly limited power supply. T h e m i n i m u m power required to operate such a system is dictated by the basic requirements pertinent to the physical realization of the elementary digital net-works. This paper presents a unified concept on these requirements to provide a common basis for evaluating the merits and limitations of the large variety of presently available and prospective digital devices and circuit techniques proposed for the implementation of practical low-power digital systems. T h e digital information processing machines may be categorically represented by a simple, abstract model illustrated in Fig. ι. T h e output information, # 1 , #2, . . . #» are specific, prescribed functions of the current input information, ai,a2 i ...a m , and the stored information, b, bz, ... bjt, 0| -a 2 -b i , b 2 , b 3 b K S t o r e d i n f o r m a t i o n Χι -x 2 M Fig. 1. Abstract model of digital system. 19 A . W . L O which are derived from previous inputs and purposely retained in the system. T h e simplicity of this model, however, only stresses the ex-tremely complex structure of such a system when the number of input variables is large, as in the case of most practical information processing machines. T h e seemingly impossible task of logically organizing and physically implementing a system of such great complexity is accom-plished through digital operation.
eBook - PDFPrinciples of Transistor Circuits
Introduction to the Design of Amplifiers, Receivers and Digital Circuits
- S W Amos, Mike James(Authors)
- 2013(Publication Date)
- Newnes(Publisher)
C H A P T E R IS Digital Circuits I N T R O D U C T I O N As mentioned in the previous two chapters, transistors in multi-vibrators and other pulse circuits are used as switches, i.e. except for the brief periods during which the transistors are changing state they are either on (taking considerable current) or off (non-con-ductive). For most of the time therefore the collector (or drain) voltage has one of two possible values namely a low value near emitter or source potential (when the transistor is on) and a high value near the supply potential (when the transistor is off). A vast range of circuits has been developed during the past decade or two in which diodes and transistors are used as switches and in which the signal paths have at all times one or other of two possible voltage levels. Such circuits are used to perform mathematical and logical operations on signals in computers and similar equipment. Circuits used in this manner are known as digital (strictly binary digital) or logic circuits and the principal types are described briefly in this chapter. L O G I C LEVELS The two significant values of voltage on the signal-carrying lines are referred to as logic level 0 and logic level 1* If level 1 is more positive than level 0 the circuit is said to use the positive logic convention and if level 1 is more negative than level 0 the circuit is said to use the negative logic convention. The distinction is important because circuits can behave differently according to the logic convention * The two levels could alternatively be values of current or more generally of air pressure in pneumatic systems or fluid pressure in hydraulic systems. 285 286 Principles of Transistor Circuits chosen. This is illustrated below but it is worth stressing now that the logic convention chosen should always be stated or implicit on diagrams of logic circuits.
eBook - ePub- Herbert L. Blitzer, Karen Stein-Ferguson, Jeffrey Huang(Authors)
- 2010(Publication Date)
- Academic Press(Publisher)
CHAPTER 12 Digital CircuitsDigital photography offers the twin advantages of not requiring the consumption of supplies for every photo taken, and the ability to show the image within seconds. An additional benefit has been the ability to easily and quickly enhance images, extract information from them, and reliably move them from one location to another. In order to do this, many complex electrical elements are employed and complicated mathematics is used to assure high-quality results. In this chapter the more basic electronic circuits will be described. And since these are predicated on binary arithmetic, this too will be explained.BASIC ELECTRICITY
Electricity is the movement of electronic charge. Electrons have intrinsic electric charge, and when they move along a path, they comprise an electrical current. The impetus to get the charge to move is electrical potential. Current is measured in amperes (or amps) and electrical potential is measured in volts. By way of example, as a big rain storm builds, rain drops form, and when they start to fall the process causes an electrical charge to accumulate in the clouds. Since there is no such activity on the ground, a voltage will grow between the clouds and the ground. When the voltage gets so high that the intervening air breaks down, the charge in the clouds will flow to the ground in a lightning bolt. The voltage existed before the current flowed since voltage, as always, is measured between two points. The flow of the charge between the clouds to the ground constitutes an electrical current in the form of lightning. Each bolt dissipates some of the accumulated charge.So current is the flow of electrical charge through something and voltage is the electrical force between two points that causes the current to flow. The product of the two is the electrical power, measured in watts—watts equals amps times volts. High voltage and low current results in low power. An example is walking across the carpet in a dry room and then touching the light switch. The voltage is quite high, but the current is very small and so no real damage is done. Another example is connecting a household light bulb across a car battery. The bulb is designed to work at 110 volts, and the car battery produces only 12. Current will flow, but the bulb will not glow. The current is significant, but the voltage is low and so there is not enough power to make the bulb light up. Current goes through and voltage is across. Voltage never goes through!
eBook - ePub- Daniel Santavicca, Daniel F. Santavicca(Authors)
- 2023(Publication Date)
- CRC Press(Publisher)
We have gone several steps up the digital circuit hierarchy, starting from logic gates, then using these to build combinational logic circuits and flip-flop circuits, and then using flip-flop circuits to build more complex circuits such as the shift register and the binary counter. Continuing up the digital circuit hierarchy all the way to a complete digital computer is beyond the scope of this text, but we can briefly outline the key ingredients.The “brain” of a computer is the processor, also known as a central processing unit or CPU. An essential component of a CPU is the arithmetic logic unit (ALU). This is a circuit built from logic gates that can perform binary arithmetic – including addition and subtraction – as well as bitwise logical operations (the functions of individual logic gates). Besides the ALU, a CPU also requires a control unit (CU) and memory. The CU directs the operation of the CPU, providing instructions to the ALU and coordinating the inputs and outputs. The memory, as you can probably guess, stores digital information until it is needed.The first commercial microprocessor – a CPU microfabricated on a single chip – was the Intel 4004, released in 1971. It contained a total of 2,250 transistors, had sixteen 4-bit registers, and ran on a 740 kHz clock frequency. Intel released its first Pentium CPU in 1993 with 3.1 million transistors and a 60 MHz clock frequency. Today's CPUs have in excess of a billion transistors and clock frequencies of several GHz. For further details on CPU design, the interested reader should consult a book on computer architecture.8.7 SPECIAL TOPIC: INTRODUCTION TO QUANTUM COMPUTING
8.7.1 CLASSICAL VERSUS QUANTUM BITS
Classically, a bit contains one piece of information: whether it is a 0 or a 1. A quantum bit, or qubit, is different than a classical bit in that it can exist not only in state 0 or state 1, it can also exist in a superposition of these two states. When measured, a qubit in such a superposition will have some probability of being found in state 0 and some probability of being found in state 1. We can't directly measure the superposition; when we measure the system, we always measure it as being in either state 0 or state 1. But by repeating the measurement many times on an identically-prepared qubit, we can determine the properties of the superposition.
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