第二章习题
一、 选择题
1、小信号谐振放大器一般工作于 状态。
①甲类 ②乙类 ③丙类 ④甲、乙类
2、对小信号谐振放大器，其通频带越宽，对特定频率的选择性 。
①越好 ②不变 ③越差 ④与通频带无关
3、并联谐振回路的阻抗在谐振时，回路呈 。
①纯阻，阻抗最小 ②纯阻，阻抗最大 ③容性，阻抗最大 ④、感性，阻抗最小
4、串联谐振回路的阻抗在谐振时，回路呈 。
①纯阻，阻抗最小 ②纯阻，阻抗最大 ③容性，阻抗最小 ④感性，阻抗最大
5、LC 并联谐振回路的品质因数Qe 为： 。（其中Re 为谐振电阻） ①L R Q o e e ω= ②C R Q o e e ω= ③L
R Q o e e ω1= ④L R Q o e e ω= 6、LC 并联谐振回路的特征阻抗ρ的表达式中哪个不对 。 ①C o ωρ1= ②L o ωρ= ③C L =ρ ④L
C =ρ 7、小信号谐振放大器谐振曲线直观反映了放大器通频带的宽窄。品质因数Qe 越小，则：
①谐振曲线尖锐，通频带越窄 ②谐振曲线平坦，通频带宽
③谐振曲线尖锐，通频带越宽 ④谐振曲线越平坦，通频带越窄
8、小信号谐振放大器的负载为： 负载。
①具有谐振性质 ②纯阻 ③感性 ④容性
9、单调谐回路谐振放大器中采用中和（或失配）的目的是为了： 。
①提高选择性 ②提高稳定性 ③提高增益 ④扩展通频带
10、单级单调谐回路谐振放大器增益A vo 与回路有载品质因数Q e 的关系是：当Q e 增大 。
①A vo 减小 ②A vo 增大 ③A vo 不确定 ④A vo 不变
11、将两级电路参数相同的单回路的谐振放大器级联，若单级的通频带为BW 0.7，两级级联后
的通频带BW 0.7(2)= 。
①BW 0.7 ②7.02
112BW - ③7.02BW ④7.0BW >
12、若单级谐振放大器的通频带为BW 0.7，则双参差调谐放大器的通频带为： 。
①BW 0.7 ②7.02
112BW - ③7.02BW ④7.0BW <
二、简答题
1、小信号谐振放大器的主要性能指标有哪些？
答：小信号谐振放大器的主要性能指标是：谐振增益、通频带、选择性、稳定性等。
2、小信号谐振放大器的作用是什么？其中的选频作用由什么来实现？
答：其作用是：既选频又放大。其选频作用由谐振回路来实现。
3、小信号谐振放大器不稳定的内部原因是什么？提高稳定性的措施有哪些？
答：①谐振放大器不稳定的原因为：由于y re 不等于零，晶体管存在着内反馈。所以它
是一个“双向器件”。作为放大器工作时，y re 的反馈作用是有害的，其有害作用
是可能引起放大器自激至使其工作不稳定。
②提高稳定性的措施有：减小y re 内反馈作用（可采用中和法）；增大y L （可采用失配法）。
4、什么叫双参差调谐放大器？它是如何提高选择性和展宽频带的？
答：所谓双参差调谐，就是将两级单调谐回路放大器的谐振频率分别调整到略高于（11f f f o ?+=）和略低于（12f f f o ?-=）中心谐振频率f o 上。具有双参差调谐的放大器就为双参差调谐放大器。
如图1-17（a ）所示，由于放大器总增益等于各级电压增益的乘积，因此只要f 1和f 2取值适当，让一级频率特性的上升段与另一级频率特性的下降段刚好相互补偿，则合成的频率特性曲线在通带内可以相对平坦，且通频带较宽，而通频带以外信号的增益则迅速衰减。使其幅频特性曲线更接近于矩形，如图1-17（b ）所示。
5、多级级联之后谐振放大器的通频带和选择性（和单级谐振放大器相比）的总变化趋势是什么？
答：多级级联之后，总的选择性变好了，通频带变窄了。
6、小信号谐振放大器中的晶体管为何要用Y 参数等效电路？
答：因为在小信号谐振放大器中，放大器件、谐振系统和负载之间一般为并联形式，采用导纳可直接进行相加，运算简便，所以采用Y 参数等效电路。（Y 参数虽与频率有关，但小信号谐振放大器属窄带系统，Y 参数变化不大，可近似认为不变。）
三、计算题
1、 如下图所示电路是单调谐放大器的交流通路：
当谐振频率Z o MH f 10=时，测得晶体管Y 的参数为：
)(5.02ms j y ie += )(520ms j y fe += )(4020s j y oe μ+= 0≈re y 放大器的通频带为Z kH BW 3007.0=，谐振电压增益为A vo =50，试求电路元件参数C 、L 和R L 的值。
解：该单调谐放大器的Y 的参数等效电路为：
∵e o Q f BW =7.0 ∴3
101030010102367.0=??==BW f Q o e 又∵5021==e
fe
uo g y n n A (其中n 1=n 2=1) ∴有：ms A y g vo fe
e 41.050005.002.022≈+==
又∵L oe e g g g +=（其中oe g 根据oe oe oe C j g s j y ωμ+=+=)(4020得s g oe μ20=）
∴ms g g g oe e L 39.0=+= ∴Ω≈=k g R L
L 56.21 又∵e o e o e e C R L R Q ωω==
∴7
2310210311041.011?????===-πωωo e e o e e Q g Q R L
H H μ17.11017.16=?≈-
327
10.4110103217.6210e e e e o e o Q g Q C PF R ωωπ-???===≈? 又∵C C C oe e +=（其中oe C 根据oe oe oe C j g s j y ωμ+=+=)(4020得
F C C o oe o oe 1376
1037.610
21040--?≈??==πωω） ∴217e oe C C C PF =-≈
大学英语2题库 单选题 8、The old bridge in my hometown___ next month. A、is going to be rebuilt B、will rebuilt C、are going to be rebuilt D、are going to rebuilt 答案：A 9、I wish I could have attended the job fair yesterday, but I it. A、missed B、would miss C、miss D、will miss 答案：A 10、I thought you come to work yesterday. A、weren’t B、haven’t C、didn’t D、aren’t 答案：C 11、We shopping yesterday and had so much fun. A、went B、gone
C、going D、goes 答案：A 12、It was and I felt cold. A、wind B、windy C、hot D、sunny 答案：B 13、He very busy this week, and he free next week. A、will be; is B、is; is C、will be; will be D、is; will be 答案：D 14、These magazines___ in the library for a long time. A、have kept B、are keeping C、have been keeping D、have been kept 答案：D 15、It hard outside. Let’s not go shopping. A、is raining
大学英语1测试答案 注意：标红为答案 测验一： （AABAA BBACA CBCCA CAAAA，题目顺序随机）题目1：They have a share.
A. each； B. every 题目2：child enjoys Christmas. A. Every； B. Each 题目3：My pen is lost. This one is my A. brother； B. brother's 题目4：Have you the skirt by yourself? A. made； B. built 题目5：My room is than the one next door. A. cleaner； B. cleanner； C. cleanest 题目6：John is the of the three brothers. A. taller； B. tallest； C. tall 题目7：We've entered an agreement. A. for； B. into； C. * 题目8：He entered his son the English examination. A. for； B. into； C. * 题目9：No one saw the thief when he entered the buliding. A. for； B. into； C. * 题目10：Everyone he will win. A. believes； B. believe 题目11：Just then, the telephone rang. It rang____. A. at once； B. immediately； C. again； D. at that moment 题目12：The shop assistant found some curtain material___me.
一、完形填空（共1道小题，共50.0分） 1.Once, three fishes lived in a pond. One evening, some ___1___ passed by the pond and saw the fishes. “This pond is full of fish”, they told each other __2___. “We have never fished here before. We must come back tomorrow morning with our ___3___ and catch these fish!” So saying, the fishermen left. When the eldest of the three fishes ___4___ this, he was troubled. He called the other fishes together and said, “Did you hear ___5___ the fishermen said? We must leave this pond at once. The fishermen will return tomorrow and kill us all!” The second of the three fishes agreed. “You are right”, he said. “We must leave the pond.” But the ____6___ fish laughed. “You are worrying without reason”, he said. “We have lived in this pond all our lives, and no fisherman has ever come here. Why should these men return? I am not going ___7____ - my luck will keep me safe.” The eldest of the fishes left the pond that ___8____ evening with his entire family. The second fish saw the fishermen ____9___ in the distance early next morning and left the pond at once with all his family. The third fish refused to leave even then. The fishermen ____10___and caught all the fish left in the pond. The third fish's luck did not help him - he too was caught and killed. (232字) a. A.fishersman B.fisherman C.fishermans D.fishermen 学生答案: D; 标准答 案: D b. A.excitedly B.excited C.excite D.exciting
一、阅读理解（共1道小题，共25.0分） 1. People are so busy these days that many have no time to cook. This is a problem because many families love home cooking! A family meal brings everyone together. In some families, meals are often the only time everyone sees each other at the same time. Another reason people enjoy home cooking is that it is often a way of showing love. A parent who makes some cookies is not just satisfying a child's sweet tooth. She or he is sending a message. The message says, "I care about you enough to spend an hour making cookies that you will eat up in 15 minutes if I let you." There is also something about the smell of home cooking. The smell of home cooking pleases people of all ages. It makes most of us feel good and loved --- even if we are the ones doing the cooking! Next time you smell a cake being cooked, stop for a moment and pay attention to your mood（心情）. 1. 1. Why do few people cook now? A. They have no time. B. They can buy food. C. Many people don?t like cooking. D. They don?t like family meals. 2. A parent spends an hour making cookies____. A. just to satisfy her or his child?s sweet tooth B. only to send a message C. to let a child eat up in 15 minutes D. often to show her or his love 3. The writer thinks the smell of home cooking _____. A. makes us happy B. makes us be interested in cooking C. makes us pay attention to our mood D. makes us love others 4. What?s the main idea of this passage? A. Family meals are important. B. How to make cookies. C. People are too busy to cook D. Homemade cookies taste better. 5. Which of the following statements is NOT true according to the passage? A. There are quite a few reasons that people love home cooking. B. It becomes a problem that most families love home cooking. C. The smell of home cooking makes most of us feel good. D. A family meal can bring the family members together. 试题分值：25.0
Unit 6 I.Write the English words or expressions according to the following definitions. 1.that cannot be believed 2.not happening often 3.have or own 4. a person who buys goods or service 5. a rough outline or version 6. a single piece of news; a single artic le 7.add (sth.) in order to make a thing more attractive to look at 8.put (time or money) away for a special purpose 9.wait patiently for a chance 10.(in the habit of) doubting that sth. is true, right, etc. II ． Fill in the gaps with the words and expressions from the following : sophisticated item take in decorate draft possess harmony at intervals set aside incredible. 1.They bought many ______ modern weapons. 2.The country ______ rich mineral resources. 3.They ______ a large amount of money for special purpose. 4.They were completely ______ by his story . 5.He comes back to see us ______ regular ______. 6.There is an important ______ of news in today ’s newspaper. 7.This is the ______ of the report. It needs modifying. 8.He earns an ______ amount of money. 9.The Christmas tree was ______ with coloured lights. 10.The designer’s aim is to produce a ______ of shape and texture. III. Choose the most suitable answer. 1.During the investigation about his bribery, he was quite _____ about the amount of the money involved. A. sophisticating B. positive C. rarely D. vainly 2. He noticed that there was an interesting _____ about the movie star in the newspaper today . A. news B. periodical C. item D. draft 3.The _____of the accused man was in doubt. However, the public all wished him to be sentenced to death. A. guilt B. nature C. bulletin D. reproach 4.In a beautiful picture there is _____ between the different colors. No doubt it is his masterpiece. A. decoration B. draft C. theory D. harmony 5.All joking _____, can you swim 15 miles? A. cared for B. skeptically C. incredibly D. aside 6.After the carpet bombing, a fire soon _____ all the old wooden buildings in the neighborhood. A. consumed B. undid C. took in D. hit home
《新视野大学英语1》试卷（A） 适用班级：2013-2014第1学期重修班 I. Vocabulary and Structure (20points) Directions: Choose the best one to complete each sentence. 1. She cut her hair short and tried to ____ herself as a man. A. decorate B. disguise C. fabricate D. fake 2. She watched him ____ all the handles and gears in his automobile until she thoughts she could run it herself. A. modulate B. incorporate C. manipulate D. induce 3. The French police are legally entitled to ____ anyone's movements as they please. A. confine B. restrict C. restrain D. limit 4. Some people argue that the death ____ does not necessarily reduce the number of murders. A. fine B. cost C. punish D. penalty 5. The university ____ consists of full professors, associate professors and assistant professors. A. crew B. personnel C. faculty D. staff 6. The latest edition of The Complete Works of Lu Xun comes in sixteen ____. A. copies B. volumes C. versions D. editions 7. Many students found the book ____ : it provided them with an
《大学英语3》第2阶段在线作业试卷要求: 答题要求: 每题只有一个正确的选项。 1(5.0分) _______ these honors he received a sum of money. ?A) Except ? ?B) But ? ?C) Besides ? ?D) Outside ?
解析： 无 2(5.0分) It’s time we _______ the lecture because everybody has arrive d. ?A) will start ? ?B) shall start ? ?C) start ? ?D) started ? 3(5.0分) His salary as a driver is much higher than ______.
a porter ? ?B) is a porter ? ?C) that of a porter ? ?D) as a porter ? 4(5.0分) _______ her and then try to copy what she does. ?A) Mind ? ?B) See ? ?C) Stare at
?D) Watch ? 5(5.0分) The girl is ______ of a film star. ?A) somebody ? ?B) something ? ?C) anybody ? ?D) anyone ?
6(5.0分) The atmosphere ______ certain gases mixed together in definit e proportions. ?A) composes of ? ?B) is made up ? ?C) consists of ? ?D) makes up of ? 7(5.0分)
一、单项选择题(只有一个正确答案) 【1】It’s time ______ the fashion show. A: see B: to watch C: to see D: watch 答案: B 【2】He had some statues in his study. One was a lady ______ nothing but a bath towel. A: wore B: wears C: to wear D: wearing 答案: D 【3】Son (in the kitchen): Shall I turn on the burner? Mother: ______________. I haven’t finished peeling the pota toes. A: No, not just B: No, not yet C: No, not still D: No, not already 答案: B 【4】Many of our most deeply ______ opinions are held simply as a result of the fact that we happen to have been “brought up”to them. A: rooted B: root C: rooting D: roots 答案: A 【5】I hear that you are ______ collecting stamps. Could I have a look? A: interested in B: pleased with C: similar to D: ready for 答案: A 【6】Martin and Mary ______ their baskets of seeds on a fence outside the village. A: took B: rested C: threw D: stole
一、句子改错（共5道小题，共25.0分） 1. This is such a beautiful day that everyone around us feel like going out for a walk. A B C D A. A B. B C. C D. D 2. Neither John and his father was able to wake up early enough to catch the morning train. A B C D A. A B. B C. C D. D
3. He finds it easier to do the cooking himself than teaching his wife to cook. A B C D A. A B. B C. C D. D 4. Despite his old age, he is still very healthful and often works in the field. A B C D A. A B. B C. C D. D
5. The information which she was injured in the accident was given by Liz. A B C D A. A B. B C. C D. D 二、阅读理解（共1道小题，共50.0分）
1. Today, as in every other day of the year, more than 3,000 U.S. adolescents will smoke their first cigarette on their way to becoming regular smokers as adults. During their lifetime, it can be expected that of these 3,000 about 23 will be murdered, 30 will die in traffic accidents, and nearly 750 will be killed by a smoking-related disease. The number of deaths attributed to cigarette smoking outweighs all other factors, whether voluntary or involuntary, as a cause of death. Since the late 1970s, when daily smoking among high school seniors reached 30 percent, smoking rates among youth have declined. While the decline is impressive, several important issues must be raised. First, in the past several years, smoking rates among youth have declined very little. Second, in the late 1970s, smoking among male high school seniors exceeded that among female by nearly 10 percent. The statistic is reversing. Third, several recent studies have indicate high school dropouts have excessively high smoking rates, as much as 75 percent . Finally, though significant declines in adolescent smoking have occurred in the past decade, no definite reasons for the decline exist. Within this context, the National Cancer Institute (NCI) began its current effort to determine the most effective measures to reduce smoking levels among youth. 1. According to the author, the deaths among youth are mainly caused by _____. A. traffic accidents B. smoking-related diseases C. murder D. all of these 2. Every day there are over _____young people who will become regular smoker. A. 75 B. 23 C. 30 D. 3,000 3. By "dropout" (in paragraph 3) the author means______. A. students who failed the examination
?A) Yes，I can. ?B) Here you are. ?C) Sorry，I don’t think so. ?D) You can take it. ?A) showed ?B) has shown ?C) will show ?D) is showing 参考答案：B 解析： 无
?A) which ?B) where ?C) when ?D) that ?A) will leave ?B) leaves ?C) will have left ?D) left
—________. ?A) I want a kilo of apples ?B) You can go your own way ?C) Thanks ?D) Excuse me. I’m busy ?A) was having ?B) have ?C) have ever had ?D) had ever had ?A) of whom only 20 of these
?B) only 20 who ?C) of 20 of these who ?D) only 20 of whom ?A) Sorry，he is busy at the moment ?B) No，you can’t ?C) Sorry，you can’t ?D) I don’t know ?A) should be hurt ?B)
is hurt ?C) will be hurt ?D) is to be hurt ?A) Sorry. He’s in at the moment. ?B) Why didn’t you call earlier? ?C) Certainly. May I have your name? ?D) D. Sorry. He doesn’t want to see you. ?A) rain
大学英语一阅读理解 一、阅读理解（共505题,共101分） 1. Few laws are so effective that you can see results just days after they take effect. But in the nine days since the federal cigarette tax more than doubled—to $1. 01 per pack—smokers have jammed telephone “quit lines” acro ss the country seeking to kick the habit. This is not a surprise to public health advocates. They’ve studied the effect of state tax increases for years, finding that smokers, especially teens, are price sensitive. Nor is it a shock to the industry, which fiercely fights every tax increase. The only wonder is that so many states insist on closing their ears to the message. Tobacco taxes improve public health, health, they raise money and most particularly, they deter people from taking up the habit as teens, which is when nearly all smokers are addicted. Yet the rate of taxation varies widely. In Manhattan, for instance, which has the highest tax in the nation, a pack of Marlboro Light Kings cost ＄10.06 at one drugstore Wednesday. Charleston, S, C., where the 7-cent-a-pack tax is the lowest in the nation. The price was $4. 78. The influence is obvious. In New York, high school smoking hit a new low in the latest surveys—13.8%, far below the national average. By comparison, 26% of high school students smoke in Kentucky, Other low-tax states have similarly depressing teen-smoking records. Hal Rogers, Representative from Kentucky, like those who are against high tobacco taxes, argues that the burden of the tax falls on low-income Americans “who choose to smoke.” That’s true, But there is more reason in keeping future generations of low-income workers from getting hooked in the first place, As for today’s adults, if the new tax drives them to quit, they will have more to spend on their families, cut their risk of cancer and heart disease and feel better. （1分） (1) The text is mainly about___________. （0.2分） A.the price of cigarettes B.the rate of teen smoking C.the effect of tobacco tax increase D.the differences in tobacco tax rate 标准答案：C (2) What does the author think is a surprise? （0.2分） A.Teen smokers are price sensitive. B.Some states still keep the tobacco tax low. C.Tobacco taxes improve public health. D.Tobacco industry fiercely fights the tax rise. 标准答案：B (3) The underlined word "deter” in Paragr aph 3 most probably means . （0.2分） A.discarding B.remove C.benefit D.free 标准答案：A (4) Rogers’ attitude towards the low-income smokers might be that of . （0.2分） A.tolerance B.unconcern C.doubt D.sympathy 标准答案：D (5) What can we learn from the last paragraph? （0.2分） A.The new tax will be beneficial in the long run. B.Low-income Americans are more likely to fall ill.
16秋北邮大学英语3阶段作业
一、单项选择题（共9道小题，共90.0分） 1.下面关于 Java 的理解错误的是（）。 A.Java 是一个面向对象、平台独立、多线 程、动态的编程环境 B.Java 是一个完整的计算平台，包括完整 的程序开发环境和运行环境 C.Java 是一个通用的编程环境，使用它可 以开发完成各种计算任务的通用程序 D.Java 是一个 Web 程序开发和运行环 境，使用它只能开发 Web 应用程序 知识 点: 阶段作业一 学生答案: [D;] 标准 答案: D 得分: [10] 试题 分值: 10.0 2.(错误) 下面不是包的用途的是（ A ） A.规定一组类的对外界面 B.防止命名冲突 C.访问控制
D.方便类的查找和使用 知识 点: 阶段作业一 学生答案: [D;] 标准 答案: A 得分: [0] 试题 分值: 10.0 3.在Java中，用Package语句说明一个包时，该包的层次结构必须是（） A.与文件的结构相同 B.与文件目录的层次相同 C.与文件类型相同 D.与文件大小相同 知识 点: 阶段作业一 学生答案: [B;] 标准 答案: B 得分: [10] 试题 分值: 10.0 4.关于Eclipse透视图说法错误的是（） A.每个透视图都定义了工作台中各个视图 的初始设置和布局 B.一个工作台窗口包含多个独立的透视 图，但同一时刻只有一个透视图是对用 户可见的 C.每个透视图都有自己的视图和编辑器，
用户可以在各个透视图间切换 D.透视图的布局是可以改变的，但改变多 次后无法再恢复到初始设置 知识 点: 阶段作业一 学生答案: [D;] 标准 答案: D 得分: [10] 试题 分值: 10.0 5.(错误) 关于Eclipse工作空间说法错误的是（ C ） A.它是用户计算机磁盘上划出的一块区 域，用来存放用户的工作资料 B.它以项目为单位组织文件和目录 C.它将各种资源组织成树形结构，文件夹 位于树的根部，项目位于树枝位置 D.用户对工作空间的每次操作都能在 Eclipse集成环境中得到同步 知识 点: 阶段作业一 学生答案: [B;] 标准 答案: C 得分: [0] 试题 分值: 10.0
中国地质大学(武汉)远程与继续教育学院 大学英语2 课程作业4（共 4 次作业） 学习层次：高起专涉及单元：第7单元——第8单元 I. Find English equivalents from the two units. 1．科学技术的发展 2.互联网用户 3.出国学习 4. 一个商科专业的学生 5.自然资源 6.副院长/系主任 7. 搜索引擎8. 网页9.信息年代 10. 手机 II. Choose the best one to fill the blanks. Food is different from area to area. The French are famous for their sauces, the Italians are praised ____1__ their pasta-food from mixture of flour, eggs and water, the Germans celebrated for their sausages, but is there anything unique to eat in the United States? When you get right down to it, there’s nothing quite as ____2__as American food. Because the United States ___3__ mostly of immigrants, there is an amazing variety of foods. The United States is a vast country ____4__by many cultures and climates, and the ____5__ food of one area is often totally unlike that of another. New Mexico and Massachusetts are good examples of states that have very different traditional foods. To understand and appreciate the food in any one region, it often helps to know the area’s history. For example, New Mexico was ____6__ the home of the Pueblo Indians who lived in villages and grew native____7_ such as corn, beans, and pumpkins. Later, Spanish settlers arrived in this area. These two groups exchanged ideas and customs and passed the ____8__ on to their descendants. This intermingling (混合) of culture is evident in the food of New Mexico. Each region of the United States is unique. Louisiana has a French impact. Many Germans populate the Midwest. In ____9___around America, a tourist has the opportunity not only to visit a variety of places and see diverse landscapes, but to taste a variety of foods as well. Some may be very different. Others will taste just ___10__ home. 1. A. with B. of C. for D. at 2. A. foreign B. un-American C. common D. specific 3. A. composes B. consists C. makes up D. constitutes 4. A. protected B. affected C. influenced D. inherited 5. A. traditional B. original C. oriental D. regional 6. A. always B. often C. sometimes D. once 7. A. crops B. vegetables C. fruit D. flowers 8. A. habits B. customs C. foods D. traditions 9. A. living B. eating C. working D. traveling 10. A. as B. like C. at D. in III. Translate the following into Chinese