电工学电工电子学复习题.doc

<p>电子学复习题

一、判断题：
1. 晶体二极管的阳极电位是—２０V，阴极电位是—１０V，则该晶体二极管处于（ &nbsp;A &nbsp;）。
A．反偏 &nbsp; &nbsp;B．正偏 &nbsp; &nbsp;C．零偏 &nbsp; &nbsp;D．以上都不对
2. 当晶体三极管的两个ＰＮ结都正偏时，则晶体三极管处于（ &nbsp;C &nbsp; ）。
A．截止状态 &nbsp; &nbsp; &nbsp;B．放大状态 &nbsp; &nbsp; C．饱和状态 &nbsp; D．以上都不对
3. 在单相半波整流电路中，如果电源变压器二次电压为１００Ｖ，则负载电压将是（ &nbsp;B &nbsp;）。
A．100ｖ &nbsp; &nbsp;B．45Ｖ &nbsp; &nbsp; &nbsp; C．90Ｖ &nbsp; &nbsp; &nbsp;D．190Ｖ
4. 当逻辑函数有n个变量时，共有（ &nbsp;D &nbsp;）个变量取值组合。
A. n &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; B. 2n &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;C. n2 &nbsp; &nbsp; &nbsp; &nbsp; D. 2n
5. 在（ D ）输入情况下，“与非”运算的结果是逻辑0。
A．全部输入是0 &nbsp; &nbsp;B.任一输入是0 &nbsp; &nbsp;C.仅一输入是0 &nbsp; &nbsp;D.全部输入是1
6、三极管处于放大区时，其发射结（ B &nbsp;），集电结（ &nbsp; ）。
A. 正偏 &nbsp; &nbsp;正偏 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;B. 正偏 &nbsp; &nbsp;反偏 &nbsp; &nbsp; &nbsp; &nbsp;C. 反偏 &nbsp; &nbsp;正偏 &nbsp; &nbsp; &nbsp; &nbsp;D. 反偏 &nbsp; &nbsp;反偏
7、硅管的死区电压是（ &nbsp;C &nbsp; ）。
A. 0.2V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; B. 0.3V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; C. 0.5V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; D. 0.7V
8、选用差分电路的原因是（ &nbsp; &nbsp; A &nbsp; &nbsp; ）。
A. 减小温漂 &nbsp; &nbsp; &nbsp; &nbsp; B. 提高输入电阻 &nbsp; &nbsp; &nbsp; &nbsp;C. 稳定放大倍数 &nbsp; &nbsp; &nbsp; &nbsp;D. 减小失真
9、单相桥式整流电路，负载上的电压平均值为（ &nbsp;B &nbsp; ）。
A. 0.45U2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;B. 0.9U2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;C. 1U2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; D. 1.2U2
10、已知逻辑函数Ｙ＝ＡＢＣ＋ＣＤ，Ｙ＝１的是（ &nbsp; D &nbsp; ）
A. &nbsp;Ａ＝０，ＢＣ＝１ &nbsp; &nbsp; &nbsp; &nbsp; B. &nbsp;ＡＢ＝１，ＣＤ＝０
C. &nbsp;Ｃ＝１，Ｄ＝０ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; D. &nbsp;ＢＣ＝１，Ｄ＝１
11.某放大电路负载开路时的输出电压为4V，接入2kΩ的负载后，输出电压为2.5V，则该放大电路的输出电阻为（A ）
A，1.2kΩ &nbsp; &nbsp;B，1.6kΩ &nbsp; &nbsp;C，3.2kΩ &nbsp; &nbsp; &nbsp;D，10kΩ
12.放大电路的输入信号频率为其下限频率f1时,增益比中频率下降分贝数为（ C &nbsp;）。
A，20 &nbsp; &nbsp; &nbsp;B，7 &nbsp; &nbsp; &nbsp; C，3 &nbsp; &nbsp; &nbsp; &nbsp;D，1
13，测得NPN型硅三极管三个电极电压分别为：UB=2.8v,UE=2.1V，UC=3.6V，则该管处于（ C ）状态。
Ａ，饱和 &nbsp;Ｂ，截止 &nbsp;Ｃ，放大 &nbsp;Ｄ，击穿
14. 已知逻辑函数Ｙ＝ＡＢＣ＋ＣＤ，Ｙ＝１的是（ B &nbsp;）
A， Ａ＝０，ＢＣ＝１ &nbsp; &nbsp; B， &nbsp;ＢＣ＝１，Ｄ＝１
C， ＡＢ＝１，ＣＤ＝０ &nbsp; D， &nbsp;Ｃ＝１，Ｄ＝０
15.为了获得电压放大，同时又使得输出与输入电压同相，则应选用（ C &nbsp;）。
A，共发射极电路 &nbsp; B，共集电极电路 &nbsp; &nbsp;C，共基极电路 &nbsp;D，共漏极电路
16、放大电路如图A.30所示，已知晶体管的β=100，则该电路中三极管工作在（ B &nbsp;）
A．放大区 &nbsp; &nbsp; &nbsp; &nbsp; B. 饱和区 &nbsp; &nbsp; &nbsp; &nbsp; C. 截止区 &nbsp; &nbsp; &nbsp; &nbsp;D. 无法确定

17、图A.31所示交流通路中，三极管的rbe=3kΩ,β=100，则该电路的输入电阻R1为（ &nbsp;D &nbsp;）。
A.100Ω &nbsp; &nbsp; B.30Ω &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;C.3.1Ω &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;D.13.1Ω
18、选用差分电路的原因是（ &nbsp; &nbsp; A &nbsp; &nbsp; ）。
A.减小温漂 &nbsp; &nbsp; &nbsp; &nbsp; B.提高输入电阻 &nbsp; &nbsp; &nbsp; &nbsp;C.稳定放大倍数 &nbsp; &nbsp; &nbsp; &nbsp;D.减小失真
19、桥式整流电容滤波电路参数适合，当输入交流电压的有效值为10V，则直流输出电压值约为（ &nbsp;C ）。
A、9V &nbsp; &nbsp; B、10V &nbsp; &nbsp; C、12V &nbsp; &nbsp; D、14V
20.、二极管、门电路如图c.1所示，它是一个（B）。
A正或门　　B正与门　　C负与门　　D与非门

二、填空题
１．晶体二极管按所用的材料可分为 &nbsp; &nbsp; &nbsp; &nbsp;硅 &nbsp; &nbsp; &nbsp;和 &nbsp; &nbsp; &nbsp;锗 &nbsp; &nbsp; &nbsp; &nbsp;两类，杂质半导体按掺入的杂质不同可分为 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Ｐ型 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;和 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Ｎ型 &nbsp; &nbsp; &nbsp; &nbsp;两种。
２．表征放大器中晶体三极管的静态工作点的参数有 &nbsp; &nbsp;Ib &nbsp; &nbsp; 、 &nbsp; &nbsp;Ie &nbsp; &nbsp; 和 &nbsp; &nbsp;Uce &nbsp; &nbsp; &nbsp; 。
3. &nbsp;(101.01)2＝( &nbsp;5.25 &nbsp; )10 &nbsp; &nbsp; &nbsp; &nbsp;(1101011.101)2 = ( &nbsp;153.5 &nbsp;)8 = ( &nbsp; 6B.A &nbsp;)16
4、三极管的输出特性曲线上可以划分三个区域 &nbsp; &nbsp; 饱和区 &nbsp; &nbsp; 、 &nbsp; &nbsp;放大区 &nbsp; &nbsp; &nbsp; 、 &nbsp; &nbsp; 截止区 &nbsp; &nbsp; &nbsp;。
5、稳压二极管是利用二极管的 &nbsp; &nbsp; &nbsp; &nbsp;反向击穿 &nbsp; &nbsp; &nbsp; &nbsp; 特性工作的。
6、N型半导体中多数载流子是_ &nbsp; &nbsp;_自由电子___ &nbsp;__，P型半导体中多数载流子是__ &nbsp;_空穴_____，PN结具有____单向导通______特性。
7、集成运算放大器通常由 &nbsp; &nbsp; 输入级 &nbsp; &nbsp; 、 &nbsp; &nbsp;中间级 &nbsp; &nbsp; 、 &nbsp; &nbsp;输出级 &nbsp; &nbsp; 、 &nbsp; &nbsp;偏置电路 &nbsp; &nbsp;四个部分组成。
8、完成下列进制之间的转换：(1011.01)2 = ( &nbsp; &nbsp;11.25 &nbsp; &nbsp; &nbsp;)10 &nbsp; &nbsp; (29.25)10 = ( &nbsp; &nbsp; 11101. 01 &nbsp; &nbsp; &nbsp; )2 &nbsp; &nbsp; &nbsp; (1101011.101)2 = ( &nbsp; &nbsp; 153.5 &nbsp; &nbsp; )8 = ( &nbsp; &nbsp; 6B.A &nbsp; &nbsp; )16
9.发射结___正向________偏置，集电结__正向________偏置，则三极管处于饱和状态。
10.两级放大电路的第一级电压放大倍数为100，即电压增益为 &nbsp; 40 &nbsp; &nbsp;dB，第二级电压增益为26dB ，则两级总电压增益为 &nbsp; &nbsp;66 &nbsp; &nbsp; &nbsp;dB。
11.差分电路的两个输入端电压分别为Ui1 =2.00V,Ui2=1.98V，则该电路的差模输入电压Uid为 &nbsp; 0.02 &nbsp; &nbsp;V，共模输入电压Uic为 &nbsp; &nbsp; &nbsp; 1.99 &nbsp; &nbsp; &nbsp;V。
12.集成运算放大器在比例运算电路中工作在 线性 &nbsp;区，在比较器中工作在 &nbsp;非线性 &nbsp; &nbsp;区。
13.在放大电路中为了提高输出电阻应引入 电流 负反馈，为了降低输入电阻应引入并联 负反馈。
14、PＮ结的正向接法是Ｐ型区接电源的 &nbsp; 正 &nbsp;极，Ｎ型区接电源的 &nbsp;负 &nbsp; 极。
15．晶体二极管主要参数是 &nbsp;最大正向电流 &nbsp; &nbsp;与 &nbsp;最高反向电压 &nbsp;。
16．Ｎ型半导体主要靠 &nbsp; &nbsp;电子 &nbsp; 来导电，Ｐ型半导体主要靠 &nbsp;空穴 &nbsp; 来导电。
17．晶体三极管低频小信号电压放大电路通常采用 &nbsp; &nbsp;阻容 &nbsp; &nbsp; &nbsp;耦合电路．
18.本征半导体中掺入微量_____三______价元素可形成P型半导体，其多数载流子为____空穴_____。
19.十进制数236对应的二进制数是_11101100___。
20.温度升高时，三极管的穿透电流Iceo将____增大______，电流放大系数β将_____增大______,发射结压降UBE将_____减小__________。
21.对于共发射极、共集电极、共基极三种组态放大电路，既能放大电压，也能放大电流是_____共发射极________放大电路；可以放大电压但不能放大电流为是_____共基极_________放大电路；只能放大电流但不能放大电压的是_____共集电极________放大电路。
22.放大电路中若要引入负反馈，现已知信号源为电流源，则应引入____并联_______负反馈；若要求提高负载能力，则应引入_______电压_________负反馈，若要求向信号索取的电流尽可能小、输出电流稳定则应引入______电流串联________负反馈。

三、计算题
1.写出下图所示各电路的输出电压值，设二极管导通电压UD＝0.7V。

&nbsp; &nbsp;

解：UO1≈1.3V， &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
UO2＝0， &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
UO3≈－1.3V， &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
2. 试总结晶体三极管分别工作在放大、饱和、截止三种工作状态时，三极管中的两个PN结所具有的特点。
解：三极管工作在放大工作状态时，集电结反偏，发射结正偏。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
三极管工作在饱和工作状态时，发射线和集电结均正偏。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
三极管工作在截止工作状态时，发射线和集电结均反偏 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

3.试写出下图各逻辑电路图的逻辑表达式。

解：图（a） &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
图（b） &nbsp; &nbsp; &nbsp;

4. 电路如图所示，已知IC=1.5 mA， UCC = 12V，β=37.5，rbe=1 kΩ，输出端开路，若要求= -150，求该电路的RB 和RC值。

解：由于 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
则(KΩ) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

5.如图电路，根据电路化简逻辑表达式，判断电路的功能。

解：

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

当输入A、B、C中有2个或3个为1时，输出F为1，否则输出F为0。所以这个电路实际上是一种3人表决用的组合电路：只要有2票或3票同意，表决就通过。 &nbsp; &nbsp; &nbsp;5分

6. 证明下列恒等式：
（1） &nbsp;
证：

（2）
&nbsp;
证：

7. 用卡诺图法化简函数： &nbsp; &nbsp;

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

8. 判断下列电路中电阻Rf的反馈类型（注明是电压还是电流、串联还是并联、正反馈还是负反馈）

电压串联负反馈

&nbsp; &nbsp;

电压并联负反馈

9. 共射放大电路如下图所示。已知：VCC＝12V，β=50 ，Rb=300kΩ,Rc=3kΩ，RL=3kΩ。
（1）求出静态工作点；
（2）求电压放大倍数、输入电阻、输出电阻。 &nbsp; &nbsp; 解：（1）
+

+

+

CC

R

b

V

+

u

o

-

u

+

-

i

Rc

C2

C2

RL

——(1’)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;——(1’)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;——(1’)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;——(1’)
（2） &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ——(2’)

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;——(2’)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;——(1’)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;——(1’)

10. 用与非门设计一个交通报警控制电路。交通信号灯有红、绿、黄3种，3种灯分别单独工作或黄、绿灯同时工作时属正常情况，其他情况均属故障，出现故障时输出报警信号。
解：（1）设红、绿、黄灯分别用A、B、C表示，灯亮时其值为1，灯灭时其值为0；输出报警信号用F表示，灯正常工作时其值为0，灯出现故障时其值为1。 &nbsp; &nbsp; &nbsp; （2’）
（2）列真值表： &nbsp; （5’）

（3）根据真值表，列出表达式并化简： (5’)

（4）画逻辑图： &nbsp;(3’)

11.二极管电路如图A.1所示，设备二极管均具有理想特性，试判断图中各二极管是导通还是截止，并求出UAO值。

答：（a）导通 &nbsp;UAO=15V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;(b)V1截止，V2导通，UAO=-6V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

12、三极管放大电路如图A.4所示，已经三极管的UBEQ=0.7V，β=100，各电容在工作频率上的容抗可略去。（1）求静态工作ICQ，UCEQ；（2）画出放大电路的微变等效电路；（3）求电压放大倍数AM=；（4）求输入电阻Ri和输出电阻R。。

解：（1）ICQ=2.2mA &nbsp;UCEQ=2.1V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; （2）放大电路的微变等效电路如图B—2所示 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; （3）An=-107 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; （4）Ri=1.27kΩ &nbsp;Ro=3kΩ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

13 试总结晶体三极管分别工作在放大、饱和、截止三种工作状态时，三极管中的两个PN结所具有的特点。

解：三极管工作在放大工作状态时，集电结反偏，发射结下偏。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
三极管工作在饱和工作状态时，发射线和集电结均正偏。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
三极管工作在截止工作状态时，发射线和集电结均反偏。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

14 在图所示电路中，由于电路参数不同，在信号源电压为正弦波时，测得输出波形如图（a）、（b）、（c）所示，试说明电路分别产生了什么失真，如何消除。

&nbsp; &nbsp;解：（a）饱和失真，增大Rb，减小Rc 。
&nbsp; &nbsp;（b）截止失真，减小Rb 。
&nbsp; &nbsp;（c）同时出现饱和失真和截止失真，应增大VCC。

15、电路如图所示，晶体管导通时UBE＝0.7V，β=50。试分析VBB为0V、1V、1.5V三种情况下T的工作
状态及输出电压uO的值。
&nbsp; &nbsp;解：（1）当VBB＝0时，T截止，uO＝12V。 &nbsp; &nbsp; &nbsp;3分
&nbsp; &nbsp;（2）当VBB＝1V时，因为 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;μA
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
所以T处于放大状态。 &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;（3）当VBB＝3V时，因为
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; μA &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
所以T处于饱和状态。

16．图示电路，已知，kΩ，kΩ，kΩ，kΩ，，试求：
（1）RL接入和断开两种情况下电路的电压放大倍数；
（2）输入电阻Ri和输出电阻Ro；
（3）输出端开路时的源电压放大倍数。

解：先求静态工作点
μA

再求三极管的动态输入电阻
ΩkΩ

（1）RL接入时的电压放大倍数为： &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

RL断开时的电压放大倍数为：

（2）输入电阻Ri为： &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
kΩ
输出电阻Ro为：
kΩ
（3） &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

17、 有两只稳压管DZ1、DZ2，其稳定电压分别为8.5V和6.5V，其正向压降均为0.5V，输入电压足够大。现欲获得7V、15V和9V的稳定输出电压UO，试画出相应的并联型稳压电路。
解：对两个稳压管采用不同的联接方式就可得到7V、15V和9V三个稳定的输出电压，电路如下图所示。

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

18、二极管电路如图A.32（a）、（b）所示，、设二极管正向管压降为0.7V，试求I1、I2、I3及UAO

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 图 &nbsp;A.32

解：(a) I1=0 &nbsp; I2=I3=1.3 m A &nbsp; &nbsp; UAO=1.4V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(b)I1=18.9 m A &nbsp;I2=4 m A &nbsp;I3=14.3 m A &nbsp;UAO=14.3V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

19计算图所示电路的电位UY（设D为理想二极管）。
（1）UA＝UB＝0时；
（2）UA＝E，UB＝0时；
（3）UA＝UB＝E时。

解
（1）由于UA＝UB＝0，DA和DB均处于截止状态，所以UY＝0； &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
（2）由UA＝E，UB＝0可知，DA导通，DB截止，所以UY＝＝E； &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
（3）由于UA＝UB＝E，DA和DB同时导通，因此UY＝＝E。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</p>