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UNIT 1 Microelectronics and Electronic Circuits
1-1 Introduction to Microelectronics
The exploring of space and the development of earth satellites have increased the importance of reducing the size and weight of electronic circuits. Also, even though electricity flows quite rapidly in computers, the time delay of the signal in the interconnections between electronic components is an important consideration. If the interconnections are reduced in size, a computer can perform operations at a faster speed.
Microelectronics involves the miniaturization of regular electronic circuits. A complete electronic circuit, an operational amplifier for example, which contains large numbers of individual interconnected components, such as diodes, resistors, transistors, etc. may be formed on a very small single substrate. The complete miniaturized circuit is then called an integrated circuit(IC).
Integrated circuits are small, light, rugged, and reliable. They require less power and lower voltages than equivalent macroscopic circuits; consequently they operate at lower temperatures, and individual components may be close together without exceeding the operating temperature limit. Relatively little stray capacitance and short time delays are produced because of the short interconnections between the individual components in the IC. Maintenance is simplified because if a component of the IC fails the complete IC is usually replaced. Mass production techniques of plane technology have reduced the cost of many ICs so that they are almost as inexpensive as a single transistor. Eventually most conventional circuits will be replaced by the IC.
There are two types of basic integrated circuit: monolithic integrated circuit and the thin or thick film. Monolithic ICs are constructed in a single substrate of single crystal semiconductor, usually silicon. Thin or thick film ICs are formed on the surface of an insulating material such as glass or a ceramic. Hybrid IC contains more than a single substrate, the term hybrid is also applied to combinations of monolithic and thin or thick film ICs.
Integrated circuits are also classified according to their functions. Digital or logical ICs are used as switches, they are either on or off. In computers the on and off states correspond to 0 or 1. Other IC is called linear or analog IC.[1] Integrated circuits can be produced using either bipolar or unique polar transistors. Field effect transistors (FET) have an advantages over bipolar transistors in many cases however. They are relatively high-impedance devices, with a corresponding reduction in current and power dissipation, and yet have high power gain. The reduction in power dissipation is particularly important where a complex circuit is to be concentrated into a small space. The problem of extracting the heat generated in the circuit may then be a difficult one.[2] The form of construction of the FET, and particularly the MOSFET, also lends itself well to integrated circuit fabrication, and enables resistors and capacitors to be included readily in the integrated circuit.
Most electronic circuits are composed of active devices, e.g. transistors and diodes, together with resistors (for bias, collector load, impedance transformation, etc.) and capacitors (e.g. for coupling ac signals while blocking dc supplies). Each of these elements can be produced in a form suitable for integrated circuit inclusion within limitations, e.g. capacitance values must not be too large. Some elements are difficult to produce in a suitable form, e.g. inductive elements, or large capacitors. Usually some alternative circuit form can be devised that dispenses with the requirement. Otherwise they must be included as an external lumped element.
KEY WORDS
microelectronics [maikruilektrniks] n. 微电子学
amplifier [mplifai] n. 放大器
bipolar(电子)[baipul] a. 双极的
bias [bais] n. 偏差;偏置
capacitor [kpsit] n. 电容器
dissipation [disipein] n. 损耗
dispense [dispens] v. 配给,免除
extract [ikstrkt] v. 抽出;释放出
fabrication [fbrikein] n. 制造,装配
FET(field effect transistors) n. 场效应晶体管
hybrid [haibrid] a. 混合的
integrate[intigreit] v. 综合;使完全
impedance [impi:dns] n. 阻抗
inductive [indktiv] a. 电感的,感应的
lumped element 集总元件
monolithic[mnliik] a. 独立的;完全统一的
silicon [silikn] n. 硅
substrate [sbstreit] n. 基片,衬底
transistor [trnzist] n. 晶体管
NOTES
[1] Integrated circuits are also classified according to their functions.Digital or logical ICs are used as switches, they are either on or off. In computers the on and off states correspond to 0 or l.Other IC is called linear or analog IC.
也可根据其功能不同对集成电路进行分类.数字IC(也称为逻辑IC)通常用作开关,表示接通或关闭.在计算中,接通和关闭状态分别对应0或1.另一种IC被称为线性或模拟IC.
[2] The reduction in power dissipation is particularly important where a complex circuit is to be concentrated into a small space. The problem of extracting the heat generated in the circuit may then be a difficult one.
对于一个复杂的电子线路集成为一小块的情况,减小功率损耗是非常重要的,要释放这种电路产生的热量将是一个难题.
EXERCISES
True/False:
(1) Because electricity flows quite rapidly in computers the time delay of the signal in the interconnections between electronic components can be ignored.( )
(2) Integrated circuits require less power and lower voltages than equivalent macroscopic circuits; consequently they operate at lower temperatures, and individual components may be close together without exceeding the operating temperature limit.( )
(3) Thin or thick film ICs are constructed in a single substrate of single crystal semiconductor. Monolithic ICs are formed on the surface of an insulating material such as glass or a ceramic.( )
(4) Because digital or logical ICs are either on or off, they can be used as switches.( )
(5) Capacitance values must not be too large in order to be suitable for integrated circuit inclusion within limitations.( )
1-2 How Does a Logic Gate in a Microchip Work
A gate seems like a device that must swing open and closed, yet microchips are etched onto silicon wafers that have no moving parts. So how can the gate open and close
Larry Wissel, ASIC Applications Engineer at IBM Microelectronics, replies:
"Those of us who design logic gates for computers seldom reminisce on how the terms we use to describe technology came into use. The vision of a gate swinging back and forth clearly does not literally represent the structures on a silicon chip. But the reason for the usage of the term 'gate' for computer logic can be appreciated by examining the basic function of a gate: to control a flow."
"On a farm, gates may be used to control the 'flow' of sheep or goats between pens. In this case, the gate consists of a physical barrier whose position is controlled by a fanner. The farmer makes a decision about the flow of animals and then moves the physical barrier to permit the desired flow."
"In a computer, a gate controls the flow of electric current through a circuit. The gate consists of transistors; the transistors are selected by the chip designer from two basic types (PMOS and NMOS transistors) that are found in the ubiquitous CMOS (complementary metal-oxide semiconductor) technology.[1]The current that flows through a gate establishes a voltage at a particular point in the circuit. This voltage represents a single 'bit' of information. The voltage may either be high (representing the value '1') or low (representing the value '0')."
"To establish a 1 on a circuit, the current flow is steered to the circuit (controlled) by 'turning on' a PMOS transistor connected between the circuit and the positive supply voltage. The supply voltage is usually an industry-standard value such as 3.3 or 5.0 volts. For the very brief interval that is required for a logic gate to switch (on the order of a nanosecond, or a billionth of a second), current will flow through a PMOS transistor from the positive power supply to the circuit."
"The current flow that charges the circuit node to a 0 is steered away from the circuit through a different kind of transistor (NMOS) connected between the circuit and the negative supply voltage, or electrical ground. Again, current will flow through the NMOS transistor for a very brief interval, but for the NMOS the current is between the circuit and the negative supply. In either case, the current flow results in a change in the circuit voltage that represents a bit of information. So, when a gate is controlling current flow, it is actually controlling the flow of information."
"Returning to the analogy between the farm and the computer chip, it is obvious that the flow is different (farm animals compared to information) and that the gate itself is different (a physical barrier compared to a transistor in the CMOS technology). But the most important difference is the means of controlling the flow. On the farm, the farmer resets the gate location by making a decision and then moving a physical barrier. A flow of animals through a complex maze of gates would require a farm hand at each gate."
"But in a computer chip, the control mechanism is the voltage on the control terminal of a transistor. This voltage turns on a transistor by changing its characteristics from that of an open circuit (the 'off' position) to one that can conduct a small current. This control voltage, in turn, is already available within the chip as a voltage at a point on another circuit. And, being a voltage on a circuit, this control mechanism represents a different bit of information."
"The overwhelming computing power of logic gates stems from the fact that the output of any particular gate is a voltage, which can in turn be used to control another gate. [2] A computer chip therefore can be designed to make complex decisions about the information flow within itself. This ability enables sophisticated systems to be created by interconnecting as many as a million gates within a single chip. All of this with no farm hands and no moving parts."
Tak Ning of the IBM T.J. Watson Research Center adds some complementary details:
"A logic gate in a microchip is made up of a specific arrangement of transistors. For modern microchips, the transistors are of the kind called metal-oxide-semiconductor field-effect transistor (MOSFET), and the semiconductor used is silicon. A MOSFET has three components or regions: a source region, a drain region and a channel region having a gate over it. The three regions are arranged horizontally adjacent to one another, with the channel region in the middle."
"In a logic gate arrangement, each of the MOSFETs works like a switch. The switch is closed, or the MOSFET is turned on, if electric current can flow readily from the source to the drain. The switch is open, or the MOSFET is turned off, if electric current cannot flow from the source to the drain." [3]
"The source and drain regions of a MOSFET are fabricated to be full of electrons which are ready to carry current. The channel region, on the other hand, is designed to be empty of electrons under normal condition, blocking the movement of current. Hence, under normal condition, the MOSFET is 'off' (or 'open') and no current can flow from the source to the drain."
"If a positive voltage is applied to the gate (which sits on top of the channel region), then electrons, which are negative charges, will be attracted toward the gate. These electrons are collected in the channel region of the MOSFET. The larger the gate voltage, the larger the concentration of electrons in the channel region. The substantial concentration of electrons in the channel provides a path by which the electrons can move easily from the source to the drain. When that happens, the MOSFET is 'on' (or 'closed') and current can flow from the source to the drain freely".
"In summary, a MOSFET in a microchip is turned on by applying a voltage to the gate to attract electrons to the channel region, and turned off by applying a voltage to the gate to repel electrons away from the channel region. There is movement of charges in the silicon, but there are no mechanical moving parts involved."[4]
What's a MOSFET
MOSFET stands for metal-oxide-semiconductor field-effect transistor. It's a kind of transistor that clips gradually when overdriven, as most tubes do.
Both tubes and transistors amplify signals by passing current from one side of the device to the other, sculpting it along the way to the same shape as a much weaker input signal. It's like a movie or slide projector - a source of energy (the bulb) is shaped by the film, and projected on the screen, where we see a much bigger version of the image on the film (even though the actual light we see comes from the bulb, not the film).
There are basically three kinds of transistor that are used to amplify audio: the most common is a bipolar transistor. It is a sandwich of three layers of silicon, with the outer ones negatively charged and the middle one positively charged (NPN), on the other way around (PNP). A small signal on the middle layer controls a much bigger current passing between the two outer layers.
A later development was the field-effect transistor (FET). Here the current doesn't have to pass through the middle layer of the sandwich. It passes near it, and is controlled by the field effect exerted on it. This was more efficient in a number of ways. It also happens to clip more softly than a bipolar transistor.
The third type is an FET where the element doing the controlling doesn't even contact the channel carrying the large current. It's insulated with a thin layer of silicon dioxide. This is the MOSFET, and it clips very softly.
The clipping characteristics of individual vacuum tube or solid-state semiconductors are by no means the whole story in the behavior of a circuit. You've probably noticed by now that a circuit with a tube in it can produce a sound that's buzzier and harsher than another that's made up of bipolar transistors. And the sound that formed the original criterion for what's desirable in overdrive, the sound of a cranked non-master-volume tube amp, has got to do with a lot things besides the tubes. There are transformers, speakers and the interaction of these with the tubes, to say nothing of the acoustic and psycho-acoustic biproducts of playing loud. Anyone interested in getting a repeatable sound that isn't dependant on playing at a certain sound pressure level would be better off discarding the dogma surrounding tubes and transistors, and employing the only devices that can be trusted-the ears.
KEY WORDS
CMOS (complementary metal-oxide semiconductor) 互补金属氧化物半导体
involved [invlvd] a. 繁杂的,受牵扯的
MOSFET (metal-oxide-semiconductor field-effect transistor)
金属氧化物半导体场效 应晶体管
reminisce [reminis] v. 缅怀往事,话旧
steer [sti] v. 掌舵,操纵,驾驶
ubiquitous [ju: bikwits] a. 无处不在的
wafer [weif] n. 晶片,圆片
NOTES
[1] The gate consists of transistors;the transistors are selected by the chip designer from two basic types(PMOS and NMOS transistors)that are found in the ubiquitous CMOS (complementary metal-oxide semiconductor) technology.
门电路由晶体管组成,而这些晶体管是由芯片设计者从广泛应用的CMOS(互补金属氧化物半导体)技术中出现的两种基本类型的晶体管(PMOS晶体管和NMOS晶体管)中选择的.
[2] The overwhelming computing power of logic gates stems from the fact that the output of any particular gate is a voltage, which can in turn be used to control another gate.
逻辑门电路的强大计算能力源于这样一个事实,即任何门电路的输出都是一个电压信号,这个电压又可以用来控制另外的门电路.
[3] In a logic gate arrangement, each of the MOSFETs works like a switch.The switch is closed, or the MOSFET is turned on, if electric current can flow readily from the source to the drain.The switch is open, or the MOSFET is turned off, if electric current cannot flow from the source to the drain.
在逻辑门电路的排列中,每一个金属氧化物半导体场效应晶体管就像一个开关一样工作.如果电流可以容易地从源极流向漏极,则开关处于闭合状态,或场效应晶体管处于开启状态.如果电流不能从源极流向漏极,则开关处于断开状态,或场效应晶体管处于关闭状态.
[4] In summary, a MOSFET in a microchip is turned on by applying a voltage to the gate to attract electrons to the channel region, and turned offby applying a voltage to the gate to repel electrons away from the channel region. There is movement of charges in the silicon, but there are no mechanical moving parts involved.
总之,通过给漏极加上电压把电荷吸引到沟道区域,可使微芯片中的金属氧化物半导体场效应晶体管处于开启状态;如果给栅极加载一个电压来阻止电荷,使之远离沟道区域,则场效应晶体管处于关闭状态.硅片中有电荷的运动,但并不涉及任何移动的机械部件.
EXERCISES
1. According to prof. Larry Wissel's replies, answer the following questions.
(1) In the third paragraph, "a single 'bit' of information" means______.
A. a voltage at a particular point in the circuit
B. two basic types (PMOS and NMOS) of transistors
C. one kind of the two basic types (PMOS and NMOS) of transistors
D. high (representing the value '1') or low (representing the value '0' ) voltage which can be used as a signal in a computer
(2) According to the passage, the control mechanism in a computer chip is _____.
A. the voltage on the control terminal of a transistor
B. the decision to move the physical barrier
C. the voltage at a particular point in the circuit
D. the means of controlling the flow
(3) Studying of the analogy between the farm and the computer chip, it is obvious that _____.
A. the flow is different B. the gate itself is different
C. the means of controlling the flow is different D. all of the above
(4) The overwhelming computing power of logic gates stems from the fact that the output of any particular gate is ____.
A. a voltage which can in turn be used to control another gate
B. an open circuit that can conduct a small current
C. a transistor in the CMOS technology
D. an industry-standard value such as 3.3 or 5.0 volts
(5) A computer can make complex decisions because ______.
A. any gate can in turn be used to control another gate
B. a transistor in the CMOS technology consumes less power
C. a PMOS transistor connects to power supply
D. an NMOS transistor connects to negative supply voltage
2. According to prof. Tak Ning's complementary details, answer the following questions.
(1) A MOSFET has three components, or regions: ______.
A. a source region, a drain region and a channel region having three gates over it
B. a source region, a drain region and a channel region having a gate over it
C. a transmit region, a drain region and a base region having a gate over it
D. a source region, a transmit region and a channel region having three gates over it
(2) The three regions are arranged horizontally adjacent to one another, with ____in the middle.
A. the transmit region B. the source region
C. the channel region D. the drain region
(3) ____ is designed to be empty of electrons under normal condition, blocking the movement of current.
A. The transmit region B. The source region
C. The channel region D. The drain region
(4) Under normal condition, the MOSFET is ____ from the source to the drain.
A. "off" (or "close") and the current can flow
B. "off" (or "open") and no current can flow
C. "on" (or "open") and the current can flow
D. "on" (or "close") and no current can flow
(5) The substantial concentration of electrons in the channel provides a path by which the electrons can move easily from_____.
A. the source to the drain B. the channel to the drain
C. the source to the channel D. the channel to the other side of the channel
3. According to passage "What's a MOSFET ", answer the following questions.
(1) MOSFET stands for metal-oxide-semiconductor field-effect transistor, it's a kind of ______.
A. tube B. PNP
C. transistor D. NPN
(2) There are basically three kinds of transistors that are used to amplify audio: the most common is______.
A. a bipolar transistor B. a PNP type transistor
C. an NPN type transistor D. a tripolar transistor
(3) To amplify a signal by a MOSFET means ________.
A. a big signal on the middle layer controls a much smaller current passing between the two outer layers
B. a small signal on the middle layer controls a much bigger current passing between the two outer layers
C. a small signal between the two outer layers controls a much bigger current passing the middle layer
D. a big signal between the two outer layers controls a much smaller current passing the middle layer
(4) A later development was the field-effect transistor (FET), here the current _____.
A. doesn't have to pass through the middle layer of the sandwich
B. passes near it
C. is controlled by the field effect exerted on it
D. all of the above
(5) "The clipping characteristics of individual vacuum tube or solid-state semiconductors are by no means the whole story in the behavior of a circuit." The writer means _____.
A. clipping characteristics of individual vacuum tube are the same as work in a circuit
B. clipping characteristics of solid-state semiconductors are better than the behavior of a circuit
C. clipping characteristics of individual vacuum tube are worse man the behavior of a circuit
D. none of the above
1-3 General Electronics Dircuits
1. Power-Supply Circuits
Most electronic equipment requires DC voltages for its operation. These can be provided by batteries or by internal power supplies that convert alternating current as available at the home electric outlet into regulated DC voltages. The first element in an internal DC power supply is a transformer, which steps up or steps down the input voltage to a level suitable for the operation of the equipment. A secondary function of the transformer is to provide electrical ground insulation of the device from the power line to reduce potential shock hazards. The transformer is then followed by a rectifier, normally a diode. In the past, vacuum diodes and a wide variety of different materials such as germanium crystals or cadmium sulfide were employed in the low-power rectifiers used in electronic equipment. Today silicon rectifiers are used almost exclusively because of their low cost and their high reliability.
Fluctuations and ripples superimposed on the rectified DC voltage (noticeable as a hum in a malfunctioning audio amplifier) can be filtered out by a capacitor; the larger the capacitor, the smaller the amount of ripple in the voltage. More precise control over voltage levels and ripples can be achieved by a voltage regulator, which also makes the internal voltages independent of fluctuations that may be encountered at an outlet. A simple, often-used voltage regulator is the zener diode. It consists of a solid-state p-n-junction diode, which acts as an insulator up to a predetermined voltage; above that voltage it becomes a conductor that bypasses excess voltages. More sophisticated voltage regulators are usually constructed as integrated circuits.
2. Amplifier Circuits
Electronic amplifiers are used mainly to increase the voltage, current, or power of a signal. A linear amplifier provides signal amplification with little or no distortion, so that the output is proportional to the input. A nonlinear amplifier may produce a considerable change in the waveform of the signal. Linear amplifiers are used for audio and video signals, whereas nonlinear amplifiers find use in oscillators, power electronics, modulators, mixers, logic circuits, and other applications where an amplitude cutoff is desired. Although vacuum tubes played a major role in amplifiers in the past, today either discrete transistor circuits or integrated circuits are mostly used.
(1) Audio Amplifiers
Audio amplifiers, such as are found in radios, television sets, citizens band (CB) radios, and cassette recorders, are generally operated at frequencies below 20 kilohertz (1 kHz = 1000 cycles/sec). They amplify the electrical signal, which then is converted to sound in a loudspeaker. Operational amplifiers (op-amps), built with integrated circuits and consisting of DC-coupled, multistage, linear amplifiers, are popular for audio amplifiers.
(2) Video Amplifiers
Video amplifiers are used mainly for signals with a frequency spectrum range up to 6 megahertz (1 MHz = 1 million cycles/sec). The signal handled by the amplifier becomes the visual information presented on the television screen, with the signal amplitude regulating the brightness of the spot forming the image on the screen. To achieve its function, a video amplifier must operate over a wide band and amplify all frequencies equally and with low distortion.
(3) Radio Frequency Amplifiers
These amplifiers boost the signal level of radio or television communication systems. Their frequencies generally range from 100 kHz to 1 GHz (1 billion cycles/sec = 1 gigahertz) and can extend well into the microwave frequency range.
3. Oscillators
Oscillators generally consist of an amplifier and some type of feedback. The output signal is fed back to the input of the amplifier. The frequency-determining elements may be a tuned inductance-capacitance circuit or a vibrating crystal. Crystal-controlled oscillators offer the highest precision and stability. Oscillators are used to produce audio and radio signals for a wide variety of purposes. For example, simple audio-frequency oscillators are used in modern push-button telephones to transmit data to the central telephone station for dialing. Audio tones generated by oscillators are also found in alarm clocks, radios, electronic organs, computers, and warning systems. High-frequency oscillators are used in communications equipment to provide tuning and signal-detection functions. Radio and television stations use precise high-frequency oscillators to produce transmitting frequencies.
4. Switching and Timing Circuits
Switching and timing circuits, or logic circuits, form the heart of any device where signals must be selected or combined in a controlled manner. Applications of these circuits include telephone switching, satellite transmissions, and digital computer operations.
Digital logic is a rational process for making simple "true" or "false" decisions based on the rules of Boolean algebra. "True" can be represented by a "1" and "false" by a "0", and in logic circuits the numerals appear as signals of two different voltages. Logic circuits are used to make specific true-false decisions based on the presence of multiple true-false signals at the inputs. The signals may be generated by mechanical switches or by solid-state transducers. Once the input signal has been accepted and conditioned (to remove unwanted electrical signals, or "noise"), it is processed by the digital logic circuits. The various families of digital logic devices, usually integrated circuits, perform a variety of logic functions through logic gates, including "OR", "AND", and "NOT", and combinations of these (such as "NOR", which includes both OR and NOT). One widely used logic family is the transistor-transistor logic (TTL). Another family is the complementary metal oxide semiconductor logic (CMOS), which performs similar functions at very low power levels but at slightly lower operating speeds. Several other less popular families of logic circuits exist, including the currently obsolete resistor-transistor logic (RTL) and the emitter coupled logic (ECL), the latter used for very-high-speed systems.
The elemental blocks in a logic device are called digital logic gates. An AND gate has two or more inputs and a single output. The output of an AND gate is true only if all the inputs are true. An OR gate has two or more inputs and a single output. The output of an OR gate is true if anyone of the inputs is true and is false if all of the inputs are false. An inverter has a single input and a single output terminal and can change a true signal to a false signal, thus performing the NOT function. More complicated logic circuits are built up from elementary gates. They include flip-flops (binary switches), counters, comparators, adders, and more complex combinations.
To perform a desired overall function, large numbers of logic elements may be connected in complex circuits. In some cases microprocessors are utilized to perform many of the switching and timing functions of the individual logic elements. The processors are specifically programmed with individual instructions to perform a given task or tasks. An advantage of microprocessors is that they make possible the performance of different logic functions, depending on the program instructions that are stored. A disadvantage of microprocessors is that normally they operate in a sequential mode, which may be too slow for some applications. In these cases specifically designed logic circuits are used.
5. Recent Developments
The development of integrated circuits has revolutionized the fields of communications, information handling, and computing. Integrated circuits reduce the size of devices and lower manufacturing and system costs, while at the same time providing high speed and increased reliability. Digital watches, hand-held computers, and electronic games are systems based on microprocessors. Other developments include the digitalization of audio signals, where the frequency and amplitude of an audio signal are coded digitally by appropriate sampling techniques, that is, techniques for measuring the amplitude of the signal at very short intervals. Digitally recorded music shows a fidelity that is not possible using direct-recording methods. Digital playback devices of this nature have already entered the home market. Digital storage could also form the basis of home video systems and may significantly alter library storage systems, because much more information can be stored on a disk for replay on a television screen than can be contained in a book.
Medical electronics has progressed from computerized axial tomography, or the use of CAT or CT scanners, to systems that can discriminate more and more of the organs of the human body. Devices that can view blood vessels and the respiratory system have been developed as well. Ultrahigh definition television also promises to substitute for many photographic processes, because it eliminates the need for silver.
Today's researches to increase the speed and capacity of computers concentrate mainly on the improvement of integrated circuit technology and the development of even faster switching components. Very-large-scale integrated (VLSI) circuits that contain several hundred thousand components on a single chip have been developed. Very-high-speed computers are being developed in which semiconductors may be replaced by superconducting circuits using Josephson junctions and operating at temperatures near absolute zero.
KEY WORDS
adder [] n. 加法器
audio amplifier 音频放大器
blood vessel 血管
Boolean algebra 布尔代数
cadmium sulfide 硫化镉
comparator n. 比较器
cassette recorder 盒式录音机
citizens band 民用波段
counter [kaunt] n. 计数器
CT(computerized tomography) n. 计算机断层造影术,CT检查
DC-coupled a. 直流耦合的,直接耦合的
definition [definin] n. 清晰度,分辨率
discriminate [diskrimineit] v. 区别,区分,区别对待
distortion [dist:n] n. 扭曲,变形,曲解
electronic organ 电子琴
emitter coupled logic (ECL) 发射极耦合逻辑(电路)
fidelity [fideliti] n. 保真度
filter ['filt] v. 过滤,滤波;n. 过滤器,滤波器
flip-flop n. 触发器
inverter [inv:t] n. 反相器
malfunction [m] n. 故障,失灵;v. 发生故障,不起作用
mixer [miks] n. 混合器,混频器
modulator [mdjuleit] n. 调制器
obsolete [bsli:t] a. 荒废的,成废物的,陈旧的
operational amplifier (op-amp) 运算放大器
oscillator [sileit] n. 振荡器
radio frequency amplifier 射频放大器
regulator [regjuleit] n. 调节器,稳压器
resistor-transistor logic (RTL) 电阻-晶体管逻辑(电路)
respiratory [rispairtri] a. 呼吸的
ripple [ripl] n. 涟波,波纹
superconducting [sju:pknd] a. 超导的
transistor-transistor logic (TTL) 晶体管-晶体管逻辑(电路)
tune [tju:n] v. 为……调谐,对准频率
very-large-scale integrated (VLSI) circuit 超大规模集成电路
video amplifier 视频放大器
warning system 报警系统
zener diode 齐纳二极管,稳压二极管
EXERCISES
True/False:
(1) The transformer in an internal DC power supply can insulate the device from the power line.( )
(2) A diode or a capacitor can be employed as a rectifier.( )
(3) A simple, often-used voltage regulator can be constructed with a zener diode.( )
(4) We can use electronic amplifiers to intensify the voltage, current and power of a signal. ( )
(5) Operational amplifiers (op-amps), built with integrated circuits and consisting of DC-coupled, multistage, linear amplifiers, are popular for audio amplifiers.( )
(6) Providing a sufficient output power is mentioned in the text as a main requirement for a video amplifier.( )
(7)Tuned inductance-capacitance circuits or vibrating crystals are used in oscillators to determine the oscillating frequency.( )
(8) The word of "rational" in the sentence "Digital logic is a rational process for making simple 'true' or 'false' decisions based on the rules of Boolean algebra." could be replaced by "inferential".( )
(9) Both RTL and ECL are not popular today and all can be used for very-high-speed systems.( )
(10) Microprocessors can perform many of the switching and timing functions of the individual logic elements because they are specifically programmed with individual instructions to perform a given task or tasks.( )
(11) Integrated circuits reduce the size of devices, lower the system costs and provide high speed, but decrease the system reliability.( )
(12) The methods are suggested by "direct-recording methods" in the sentence "Digitally recorded music shows a fidelity that is not possible using direct-recording methods" are analogical methods.( )
(13) From the sentence "Digital storage could also form the basis of home video systems and may significantly alter library storage systems, because much more information can be stored on a disk for replay on a television screen than can be contained in a book", we can call the disk an electronic book.( )
(14) The acronym "CT" stands for Computer Tomography.( )
(15) At the end of the text, the author points out that very-high-speed computers have already existed.( )
电子信息科学专业英语导读教程
UNIT 1 Microelectronics and Electronic Circuits
1-1 Introduction to Microelectronics
The exploring of space and the development of earth satellites have increased the importance of reducing the size and weight of electronic circuits. Also, even though electricity flows quite rapidly in computers, the time delay of the signal in the interconnections between electronic components is an important consideration. If the interconnections are reduced in size, a computer can perform operations at a faster speed.
Microelectronics involves the miniaturization of regular electronic circuits. A complete electronic circuit, an operational amplifier for example, which contains large numbers of individual interconnected components, such as diodes, resistors, transistors, etc. may be formed on a very small single substrate. The complete miniaturized circuit is then called an integrated circuit(IC).
Integrated circuits are small, light, rugged, and reliable. They require less power and lower voltages than equivalent macroscopic circuits; consequently they operate at lower temperatures, and individual components may be close together without exceeding the operating temperature limit. Relatively little stray capacitance and short time delays are produced because of the short interconnections between the individual components in the IC. Maintenance is simplified because if a component of the IC fails the complete IC is usually replaced. Mass production techniques of plane technology have reduced the cost of many ICs so that they are almost as inexpensive as a single transistor. Eventually most conventional circuits will be replaced by the IC.
There are two types of basic integrated circuit: monolithic integrated circuit and the thin or thick film. Monolithic ICs are constructed in a single substrate of single crystal semiconductor, usually silicon. Thin or thick film ICs are formed on the surface of an insulating material such as glass or a ceramic. Hybrid IC contains more than a single substrate, the term hybrid is also applied to combinations of monolithic and thin or thick film ICs.
Integrated circuits are also classified according to their functions. Digital or logical ICs are used as switches, they are either on or off. In computers the on and off states correspond to 0 or 1. Other IC is called linear or analog IC.[1] Integrated circuits can be produced using either bipolar or unique polar transistors. Field effect transistors (FET) have an advantages over bipolar transistors in many cases however. They are relatively high-impedance devices, with a corresponding reduction in current and power dissipation, and yet have high power gain. The reduction in power dissipation is particularly important where a complex circuit is to be concentrated into a small space. The problem of extracting the heat generated in the circuit may then be a difficult one.[2] The form of construction of the FET, and particularly the MOSFET, also lends itself well to integrated circuit fabrication, and enables resistors and capacitors to be included readily in the integrated circuit.
Most electronic circuits are composed of active devices, e.g. transistors and diodes, together with resistors (for bias, collector load, impedance transformation, etc.) and capacitors (e.g. for coupling ac signals while blocking dc supplies). Each of these elements can be produced in a form suitable for integrated circuit inclusion within limitations, e.g. capacitance values must not be too large. Some elements are difficult to produce in a suitable form, e.g. inductive elements, or large capacitors. Usually some alternative circuit form can be devised that dispenses with the requirement. Otherwise they must be included as an external lumped element.
KEY WORDS
microelectronics [maikruilektrniks] n. 微电子学
amplifier [mplifai] n. 放大器
bipolar(电子)[baipul] a. 双极的
bias [bais] n. 偏差;偏置
capacitor [kpsit] n. 电容器
dissipation [disipein] n. 损耗
dispense [dispens] v. 配给,免除
extract [ikstrkt] v. 抽出;释放出
fabrication [fbrikein] n. 制造,装配
FET(field effect transistors) n. 场效应晶体管
hybrid [haibrid] a. 混合的
integrate[intigreit] v. 综合;使完全
impedance [impi:dns] n. 阻抗
inductive [indktiv] a. 电感的,感应的
lumped element 集总元件
monolithic[mnliik] a. 独立的;完全统一的
silicon [silikn] n. 硅
substrate [sbstreit] n. 基片,衬底
transistor [trnzist] n. 晶体管
NOTES
[1] Integrated circuits are also classified according to their functions.Digital or logical ICs are used as switches, they are either on or off. In computers the on and off states correspond to 0 or l.Other IC is called linear or analog IC.
也可根据其功能不同对集成电路进行分类.数字IC(也称为逻辑IC)通常用作开关,表示接通或关闭.在计算中,接通和关闭状态分别对应0或1.另一种IC被称为线性或模拟IC.
[2] The reduction in power dissipation is particularly important where a complex circuit is to be concentrated into a small space. The problem of extracting the heat generated in the circuit may then be a difficult one.
对于一个复杂的电子线路集成为一小块的情况,减小功率损耗是非常重要的,要释放这种电路产生的热量将是一个难题.
EXERCISES
True/False:
(1) Because electricity flows quite rapidly in computers the time delay of the signal in the interconnections between electronic components can be ignored.( )
(2) Integrated circuits require less power and lower voltages than equivalent macroscopic circuits; consequently they operate at lower temperatures, and individual components may be close together without exceeding the operating temperature limit.( )
(3) Thin or thick film ICs are constructed in a single substrate of single crystal semiconductor. Monolithic ICs are formed on the surface of an insulating material such as glass or a ceramic.( )
(4) Because digital or logical ICs are either on or off, they can be used as switches.( )
(5) Capacitance values must not be too large in order to be suitable for integrated circuit inclusion within limitations.( )
1-2 How Does a Logic Gate in a Microchip Work
A gate seems like a device that must swing open and closed, yet microchips are etched onto silicon wafers that have no moving parts. So how can the gate open and close
Larry Wissel, ASIC Applications Engineer at IBM Microelectronics, replies:
"Those of us who design logic gates for computers seldom reminisce on how the terms we use to describe technology came into use. The vision of a gate swinging back and forth clearly does not literally represent the structures on a silicon chip. But the reason for the usage of the term 'gate' for computer logic can be appreciated by examining the basic function of a gate: to control a flow."
"On a farm, gates may be used to control the 'flow' of sheep or goats between pens. In this case, the gate consists of a physical barrier whose position is controlled by a fanner. The farmer makes a decision about the flow of animals and then moves the physical barrier to permit the desired flow."
"In a computer, a gate controls the flow of electric current through a circuit. The gate consists of transistors; the transistors are selected by the chip designer from two basic types (PMOS and NMOS transistors) that are found in the ubiquitous CMOS (complementary metal-oxide semiconductor) technology.[1]The current that flows through a gate establishes a voltage at a particular point in the circuit. This voltage represents a single 'bit' of information. The voltage may either be high (representing the value '1') or low (representing the value '0')."
"To establish a 1 on a circuit, the current flow is steered to the circuit (controlled) by 'turning on' a PMOS transistor connected between the circuit and the positive supply voltage. The supply voltage is usually an industry-standard value such as 3.3 or 5.0 volts. For the very brief interval that is required for a logic gate to switch (on the order of a nanosecond, or a billionth of a second), current will flow through a PMOS transistor from the positive power supply to the circuit."
"The current flow that charges the circuit node to a 0 is steered away from the circuit through a different kind of transistor (NMOS) connected between the circuit and the negative supply voltage, or electrical ground. Again, current will flow through the NMOS transistor for a very brief interval, but for the NMOS the current is between the circuit and the negative supply. In either case, the current flow results in a change in the circuit voltage that represents a bit of information. So, when a gate is controlling current flow, it is actually controlling the flow of information."
"Returning to the analogy between the farm and the computer chip, it is obvious that the flow is different (farm animals compared to information) and that the gate itself is different (a physical barrier compared to a transistor in the CMOS technology). But the most important difference is the means of controlling the flow. On the farm, the farmer resets the gate location by making a decision and then moving a physical barrier. A flow of animals through a complex maze of gates would require a farm hand at each gate."
"But in a computer chip, the control mechanism is the voltage on the control terminal of a transistor. This voltage turns on a transistor by changing its characteristics from that of an open circuit (the 'off' position) to one that can conduct a small current. This control voltage, in turn, is already available within the chip as a voltage at a point on another circuit. And, being a voltage on a circuit, this control mechanism represents a different bit of information."
"The overwhelming computing power of logic gates stems from the fact that the output of any particular gate is a voltage, which can in turn be used to control another gate. [2] A computer chip therefore can be designed to make complex decisions about the information flow within itself. This ability enables sophisticated systems to be created by interconnecting as many as a million gates within a single chip. All of this with no farm hands and no moving parts."
Tak Ning of the IBM T.J. Watson Research Center adds some complementary details:
"A logic gate in a microchip is made up of a specific arrangement of transistors. For modern microchips, the transistors are of the kind called metal-oxide-semiconductor field-effect transistor (MOSFET), and the semiconductor used is silicon. A MOSFET has three components or regions: a source region, a drain region and a channel region having a gate over it. The three regions are arranged horizontally adjacent to one another, with the channel region in the middle."
"In a logic gate arrangement, each of the MOSFETs works like a switch. The switch is closed, or the MOSFET is turned on, if electric current can flow readily from the source to the drain. The switch is open, or the MOSFET is turned off, if electric current cannot flow from the source to the drain." [3]
"The source and drain regions of a MOSFET are fabricated to be full of electrons which are ready to carry current. The channel region, on the other hand, is designed to be empty of electrons under normal condition, blocking the movement of current. Hence, under normal condition, the MOSFET is 'off' (or 'open') and no current can flow from the source to the drain."
"If a positive voltage is applied to the gate (which sits on top of the channel region), then electrons, which are negative charges, will be attracted toward the gate. These electrons are collected in the channel region of the MOSFET. The larger the gate voltage, the larger the concentration of electrons in the channel region. The substantial concentration of electrons in the channel provides a path by which the electrons can move easily from the source to the drain. When that happens, the MOSFET is 'on' (or 'closed') and current can flow from the source to the drain freely".
"In summary, a MOSFET in a microchip is turned on by applying a voltage to the gate to attract electrons to the channel region, and turned off by applying a voltage to the gate to repel electrons away from the channel region. There is movement of charges in the silicon, but there are no mechanical moving parts involved."[4]
What's a MOSFET
MOSFET stands for metal-oxide-semiconductor field-effect transistor. It's a kind of transistor that clips gradually when overdriven, as most tubes do.
Both tubes and transistors amplify signals by passing current from one side of the device to the other, sculpting it along the way to the same shape as a much weaker input signal. It's like a movie or slide projector - a source of energy (the bulb) is shaped by the film, and projected on the screen, where we see a much bigger version of the image on the film (even though the actual light we see comes from the bulb, not the film).
There are basically three kinds of transistor that are used to amplify audio: the most common is a bipolar transistor. It is a sandwich of three layers of silicon, with the outer ones negatively charged and the middle one positively charged (NPN), on the other way around (PNP). A small signal on the middle layer controls a much bigger current passing between the two outer layers.
A later development was the field-effect transistor (FET). Here the current doesn't have to pass through the middle layer of the sandwich. It passes near it, and is controlled by the field effect exerted on it. This was more efficient in a number of ways. It also happens to clip more softly than a bipolar transistor.
The third type is an FET where the element doing the controlling doesn't even contact the channel carrying the large current. It's insulated with a thin layer of silicon dioxide. This is the MOSFET, and it clips very softly.
The clipping characteristics of individual vacuum tube or solid-state semiconductors are by no means the whole story in the behavior of a circuit. You've probably noticed by now that a circuit with a tube in it can produce a sound that's buzzier and harsher than another that's made up of bipolar transistors. And the sound that formed the original criterion for what's desirable in overdrive, the sound of a cranked non-master-volume tube amp, has got to do with a lot things besides the tubes. There are transformers, speakers and the interaction of these with the tubes, to say nothing of the acoustic and psycho-acoustic biproducts of playing loud. Anyone interested in getting a repeatable sound that isn't dependant on playing at a certain sound pressure level would be better off discarding the dogma surrounding tubes and transistors, and employing the only devices that can be trusted-the ears.
KEY WORDS
CMOS (complementary metal-oxide semiconductor) 互补金属氧化物半导体
involved [invlvd] a. 繁杂的,受牵扯的
MOSFET (metal-oxide-semiconductor field-effect transistor)
金属氧化物半导体场效 应晶体管
reminisce [reminis] v. 缅怀往事,话旧
steer [sti] v. 掌舵,操纵,驾驶
ubiquitous [ju: bikwits] a. 无处不在的
wafer [weif] n. 晶片,圆片
NOTES
[1] The gate consists of transistors;the transistors are selected by the chip designer from two basic types(PMOS and NMOS transistors)that are found in the ubiquitous CMOS (complementary metal-oxide semiconductor) technology.
门电路由晶体管组成,而这些晶体管是由芯片设计者从广泛应用的CMOS(互补金属氧化物半导体)技术中出现的两种基本类型的晶体管(PMOS晶体管和NMOS晶体管)中选择的.
[2] The overwhelming computing power of logic gates stems from the fact that the output of any particular gate is a voltage, which can in turn be used to control another gate.
逻辑门电路的强大计算能力源于这样一个事实,即任何门电路的输出都是一个电压信号,这个电压又可以用来控制另外的门电路.
[3] In a logic gate arrangement, each of the MOSFETs works like a switch.The switch is closed, or the MOSFET is turned on, if electric current can flow readily from the source to the drain.The switch is open, or the MOSFET is turned off, if electric current cannot flow from the source to the drain.
在逻辑门电路的排列中,每一个金属氧化物半导体场效应晶体管就像一个开关一样工作.如果电流可以容易地从源极流向漏极,则开关处于闭合状态,或场效应晶体管处于开启状态.如果电流不能从源极流向漏极,则开关处于断开状态,或场效应晶体管处于关闭状态.
[4] In summary, a MOSFET in a microchip is turned on by applying a voltage to the gate to attract electrons to the channel region, and turned offby applying a voltage to the gate to repel electrons away from the channel region. There is movement of charges in the silicon, but there are no mechanical moving parts involved.
总之,通过给漏极加上电压把电荷吸引到沟道区域,可使微芯片中的金属氧化物半导体场效应晶体管处于开启状态;如果给栅极加载一个电压来阻止电荷,使之远离沟道区域,则场效应晶体管处于关闭状态.硅片中有电荷的运动,但并不涉及任何移动的机械部件.
EXERCISES
1. According to prof. Larry Wissel's replies, answer the following questions.
(1) In the third paragraph, "a single 'bit' of information" means______.
A. a voltage at a particular point in the circuit
B. two basic types (PMOS and NMOS) of transistors
C. one kind of the two basic types (PMOS and NMOS) of transistors
D. high (representing the value '1') or low (representing the value '0' ) voltage which can be used as a signal in a computer
(2) According to the passage, the control mechanism in a computer chip is _____.
A. the voltage on the control terminal of a transistor
B. the decision to move the physical barrier
C. the voltage at a particular point in the circuit
D. the means of controlling the flow
(3) Studying of the analogy between the farm and the computer chip, it is obvious that _____.
A. the flow is different B. the gate itself is different
C. the means of controlling the flow is different D. all of the above
(4) The overwhelming computing power of logic gates stems from the fact that the output of any particular gate is ____.
A. a voltage which can in turn be used to control another gate
B. an open circuit that can conduct a small current
C. a transistor in the CMOS technology
D. an industry-standard value such as 3.3 or 5.0 volts
(5) A computer can make complex decisions because ______.
A. any gate can in turn be used to control another gate
B. a transistor in the CMOS technology consumes less power
C. a PMOS transistor connects to power supply
D. an NMOS transistor connects to negative supply voltage
2. According to prof. Tak Ning's complementary details, answer the following questions.
(1) A MOSFET has three components, or regions: ______.
A. a source region, a drain region and a channel region having three gates over it
B. a source region, a drain region and a channel region having a gate over it
C. a transmit region, a drain region and a base region having a gate over it
D. a source region, a transmit region and a channel region having three gates over it
(2) The three regions are arranged horizontally adjacent to one another, with ____in the middle.
A. the transmit region B. the source region
C. the channel region D. the drain region
(3) ____ is designed to be empty of electrons under normal condition, blocking the movement of current.
A. The transmit region B. The source region
C. The channel region D. The drain region
(4) Under normal condition, the MOSFET is ____ from the source to the drain.
A. "off" (or "close") and the current can flow
B. "off" (or "open") and no current can flow
C. "on" (or "open") and the current can flow
D. "on" (or "close") and no current can flow
(5) The substantial concentration of electrons in the channel provides a path by which the electrons can move easily from_____.
A. the source to the drain B. the channel to the drain
C. the source to the channel D. the channel to the other side of the channel
3. According to passage "What's a MOSFET ", answer the following questions.
(1) MOSFET stands for metal-oxide-semiconductor field-effect transistor, it's a kind of ______.
A. tube B. PNP
C. transistor D. NPN
(2) There are basically three kinds of transistors that are used to amplify audio: the most common is______.
A. a bipolar transistor B. a PNP type transistor
C. an NPN type transistor D. a tripolar transistor
(3) To amplify a signal by a MOSFET means ________.
A. a big signal on the middle layer controls a much smaller current passing between the two outer layers
B. a small signal on the middle layer controls a much bigger current passing between the two outer layers
C. a small signal between the two outer layers controls a much bigger current passing the middle layer
D. a big signal between the two outer layers controls a much smaller current passing the middle layer
(4) A later development was the field-effect transistor (FET), here the current _____.
A. doesn't have to pass through the middle layer of the sandwich
B. passes near it
C. is controlled by the field effect exerted on it
D. all of the above
(5) "The clipping characteristics of individual vacuum tube or solid-state semiconductors are by no means the whole story in the behavior of a circuit." The writer means _____.
A. clipping characteristics of individual vacuum tube are the same as work in a circuit
B. clipping characteristics of solid-state semiconductors are better than the behavior of a circuit
C. clipping characteristics of individual vacuum tube are worse man the behavior of a circuit
D. none of the above
1-3 General Electronics Dircuits
1. Power-Supply Circuits
Most electronic equipment requires DC voltages for its operation. These can be provided by batteries or by internal power supplies that convert alternating current as available at the home electric outlet into regulated DC voltages. The first element in an internal DC power supply is a transformer, which steps up or steps down the input voltage to a level suitable for the operation of the equipment. A secondary function of the transformer is to provide electrical ground insulation of the device from the power line to reduce potential shock hazards. The transformer is then followed by a rectifier, normally a diode. In the past, vacuum diodes and a wide variety of different materials such as germanium crystals or cadmium sulfide were employed in the low-power rectifiers used in electronic equipment. Today silicon rectifiers are used almost exclusively because of their low cost and their high reliability.
Fluctuations and ripples superimposed on the rectified DC voltage (noticeable as a hum in a malfunctioning audio amplifier) can be filtered out by a capacitor; the larger the capacitor, the smaller the amount of ripple in the voltage. More precise control over voltage levels and ripples can be achieved by a voltage regulator, which also makes the internal voltages independent of fluctuations that may be encountered at an outlet. A simple, often-used voltage regulator is the zener diode. It consists of a solid-state p-n-junction diode, which acts as an insulator up to a predetermined voltage; above that voltage it becomes a conductor that bypasses excess voltages. More sophisticated voltage regulators are usually constructed as integrated circuits.
2. Amplifier Circuits
Electronic amplifiers are used mainly to increase the voltage, current, or power of a signal. A linear amplifier provides signal amplification with little or no distortion, so that the output is proportional to the input. A nonlinear amplifier may produce a considerable change in the waveform of the signal. Linear amplifiers are used for audio and video signals, whereas nonlinear amplifiers find use in oscillators, power electronics, modulators, mixers, logic circuits, and other applications where an amplitude cutoff is desired. Although vacuum tubes played a major role in amplifiers in the past, today either discrete transistor circuits or integrated circuits are mostly used.
(1) Audio Amplifiers
Audio amplifiers, such as are found in radios, television sets, citizens band (CB) radios, and cassette recorders, are generally operated at frequencies below 20 kilohertz (1 kHz = 1000 cycles/sec). They amplify the electrical signal, which then is converted to sound in a loudspeaker. Operational amplifiers (op-amps), built with integrated circuits and consisting of DC-coupled, multistage, linear amplifiers, are popular for audio amplifiers.
(2) Video Amplifiers
Video amplifiers are used mainly for signals with a frequency spectrum range up to 6 megahertz (1 MHz = 1 million cycles/sec). The signal handled by the amplifier becomes the visual information presented on the television screen, with the signal amplitude regulating the brightness of the spot forming the image on the screen. To achieve its function, a video amplifier must operate over a wide band and amplify all frequencies equally and with low distortion.
(3) Radio Frequency Amplifiers
These amplifiers boost the signal level of radio or television communication systems. Their frequencies generally range from 100 kHz to 1 GHz (1 billion cycles/sec = 1 gigahertz) and can extend well into the microwave frequency range.
3. Oscillators
Oscillators generally consist of an amplifier and some type of feedback. The output signal is fed back to the input of the amplifier. The frequency-determining elements may be a tuned inductance-capacitance circuit or a vibrating crystal. Crystal-controlled oscillators offer the highest precision and stability. Oscillators are used to produce audio and radio signals for a wide variety of purposes. For example, simple audio-frequency oscillators are used in modern push-button telephones to transmit data to the central telephone station for dialing. Audio tones generated by oscillators are also found in alarm clocks, radios, electronic organs, computers, and warning systems. High-frequency oscillators are used in communications equipment to provide tuning and signal-detection functions. Radio and television stations use precise high-frequency oscillators to produce transmitting frequencies.
4. Switching and Timing Circuits
Switching and timing circuits, or logic circuits, form the heart of any device where signals must be selected or combined in a controlled manner. Applications of these circuits include telephone switching, satellite transmissions, and digital computer operations.
Digital logic is a rational process for making simple "true" or "false" decisions based on the rules of Boolean algebra. "True" can be represented by a "1" and "false" by a "0", and in logic circuits the numerals appear as signals of two different voltages. Logic circuits are used to make specific true-false decisions based on the presence of multiple true-false signals at the inputs. The signals may be generated by mechanical switches or by solid-state transducers. Once the input signal has been accepted and conditioned (to remove unwanted electrical signals, or "noise"), it is processed by the digital logic circuits. The various families of digital logic devices, usually integrated circuits, perform a variety of logic functions through logic gates, including "OR", "AND", and "NOT", and combinations of these (such as "NOR", which includes both OR and NOT). One widely used logic family is the transistor-transistor logic (TTL). Another family is the complementary metal oxide semiconductor logic (CMOS), which performs similar functions at very low power levels but at slightly lower operating speeds. Several other less popular families of logic circuits exist, including the currently obsolete resistor-transistor logic (RTL) and the emitter coupled logic (ECL), the latter used for very-high-speed systems.
The elemental blocks in a logic device are called digital logic gates. An AND gate has two or more inputs and a single output. The output of an AND gate is true only if all the inputs are true. An OR gate has two or more inputs and a single output. The output of an OR gate is true if anyone of the inputs is true and is false if all of the inputs are false. An inverter has a single input and a single output terminal and can change a true signal to a false signal, thus performing the NOT function. More complicated logic circuits are built up from elementary gates. They include flip-flops (binary switches), counters, comparators, adders, and more complex combinations.
To perform a desired overall function, large numbers of logic elements may be connected in complex circuits. In some cases microprocessors are utilized to perform many of the switching and timing functions of the individual logic elements. The processors are specifically programmed with individual instructions to perform a given task or tasks. An advantage of microprocessors is that they make possible the performance of different logic functions, depending on the program instructions that are stored. A disadvantage of microprocessors is that normally they operate in a sequential mode, which may be too slow for some applications. In these cases specifically designed logic circuits are used.
5. Recent Developments
The development of integrated circuits has revolutionized the fields of communications, information handling, and computing. Integrated circuits reduce the size of devices and lower manufacturing and system costs, while at the same time providing high speed and increased reliability. Digital watches, hand-held computers, and electronic games are systems based on microprocessors. Other developments include the digitalization of audio signals, where the frequency and amplitude of an audio signal are coded digitally by appropriate sampling techniques, that is, techniques for measuring the amplitude of the signal at very short intervals. Digitally recorded music shows a fidelity that is not possible using direct-recording methods. Digital playback devices of this nature have already entered the home market. Digital storage could also form the basis of home video systems and may significantly alter library storage systems, because much more information can be stored on a disk for replay on a television screen than can be contained in a book.
Medical electronics has progressed from computerized axial tomography, or the use of CAT or CT scanners, to systems that can discriminate more and more of the organs of the human body. Devices that can view blood vessels and the respiratory system have been developed as well. Ultrahigh definition television also promises to substitute for many photographic processes, because it eliminates the need for silver.
Today's researches to increase the speed and capacity of computers concentrate mainly on the improvement of integrated circuit technology and the development of even faster switching components. Very-large-scale integrated (VLSI) circuits that contain several hundred thousand components on a single chip have been developed. Very-high-speed computers are being developed in which semiconductors may be replaced by superconducting circuits using Josephson junctions and operating at temperatures near absolute zero.
KEY WORDS
adder [] n. 加法器
audio amplifier 音频放大器
blood vessel 血管
Boolean algebra 布尔代数
cadmium sulfide 硫化镉
comparator n. 比较器
cassette recorder 盒式录音机
citizens band 民用波段
counter [kaunt] n. 计数器
CT(computerized tomography) n. 计算机断层造影术,CT检查
DC-coupled a. 直流耦合的,直接耦合的
definition [definin] n. 清晰度,分辨率
discriminate [diskrimineit] v. 区别,区分,区别对待
distortion [dist:n] n. 扭曲,变形,曲解
electronic organ 电子琴
emitter coupled logic (ECL) 发射极耦合逻辑(电路)
fidelity [fideliti] n. 保真度
filter ['filt] v. 过滤,滤波;n. 过滤器,滤波器
flip-flop n. 触发器
inverter [inv:t] n. 反相器
malfunction [m] n. 故障,失灵;v. 发生故障,不起作用
mixer [miks] n. 混合器,混频器
modulator [mdjuleit] n. 调制器
obsolete [bsli:t] a. 荒废的,成废物的,陈旧的
operational amplifier (op-amp) 运算放大器
oscillator [sileit] n. 振荡器
radio frequency amplifier 射频放大器
regulator [regjuleit] n. 调节器,稳压器
resistor-transistor logic (RTL) 电阻-晶体管逻辑(电路)
respiratory [rispairtri] a. 呼吸的
ripple [ripl] n. 涟波,波纹
superconducting [sju:pknd] a. 超导的
transistor-transistor logic (TTL) 晶体管-晶体管逻辑(电路)
tune [tju:n] v. 为……调谐,对准频率
very-large-scale integrated (VLSI) circuit 超大规模集成电路
video amplifier 视频放大器
warning system 报警系统
zener diode 齐纳二极管,稳压二极管
EXERCISES
True/False:
(1) The transformer in an internal DC power supply can insulate the device from the power line.( )
(2) A diode or a capacitor can be employed as a rectifier.( )
(3) A simple, often-used voltage regulator can be constructed with a zener diode.( )
(4) We can use electronic amplifiers to intensify the voltage, current and power of a signal. ( )
(5) Operational amplifiers (op-amps), built with integrated circuits and consisting of DC-coupled, multistage, linear amplifiers, are popular for audio amplifiers.( )
(6) Providing a sufficient output power is mentioned in the text as a main requirement for a video amplifier.( )
(7)Tuned inductance-capacitance circuits or vibrating crystals are used in oscillators to determine the oscillating frequency.( )
(8) The word of "rational" in the sentence "Digital logic is a rational process for making simple 'true' or 'false' decisions based on the rules of Boolean algebra." could be replaced by "inferential".( )
(9) Both RTL and ECL are not popular today and all can be used for very-high-speed systems.( )
(10) Microprocessors can perform many of the switching and timing functions of the individual logic elements because they are specifically programmed with individual instructions to perform a given task or tasks.( )
(11) Integrated circuits reduce the size of devices, lower the system costs and provide high speed, but decrease the system reliability.( )
(12) The methods are suggested by "direct-recording methods" in the sentence "Digitally recorded music shows a fidelity that is not possible using direct-recording methods" are analogical methods.( )
(13) From the sentence "Digital storage could also form the basis of home video systems and may significantly alter library storage systems, because much more information can be stored on a disk for replay on a television screen than can be contained in a book", we can call the disk an electronic book.( )
(14) The acronym "CT" stands for Computer Tomography.( )
(15) At the end of the text, the author points out that very-high-speed computers have already existed.( )
电子信息科学专业英语导读教程
UNIT 1 Microelectronics and Electronic Circuits
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