文档介绍：Ch8 Methods of Analysis and Selected Topics(dc)
一、电源
二、电路的基本分析方法:
支路电流法、网孔法、节点电压法
三、电桥
四、三角形星形转换
Linear(线性): the characteristics of work elements are independent of the voltage across or current through them.
Bilateral (双向): refers to the fact that there is no change in the behavior or characteristics of an element if the current through or voltage across the element is reversed.
一、复习电流源与电压源:见下页图
1.  电压源:
实际电压源可看成理想电压源与内阻串联
电压源电动势不变,流过的电流可变。(Rint=0时)
2.  电流源:
:
P250: Fig 三极管电路输入恒流,输出近似恒流
输出端电流是输入端的倍
:输出电压与外电路有关
:黑体P251 自看
-3 Fig -5 在后面自看说明电流源极性
I or t
V or t
V
I
A
B
D
C
I
V
I
V
. Find the source voltage VS and the current I1 for the Fig. . P251
Solution: I1=I=10 mA
VS=V1=I1R1=(10 mA)(20 k)=200 V
. Find the voltage Vs and the currents I1 and I2 for work of Fig.
Solution: VS=E = 12V I2=VR/R= E/R =3A
Applying Kirchhoff’s law:
I= I1 + I2 and I1 =7A-3A=4A
. Determine the current I1 and the voltage Vs for work of Fig. .
Solution: Using the current divider rule:
I1=2A,V1=4V.
KVL:
Vs-V1-20V=0 Vs=24V
Note the polarity of Vs as determined by the work.

: .
-252
黑体字:电流源与电压源等效是在他们的外部终端上(即从负载来看是等效的)等效。
内部不等效,RS上功率不同。
。见下页图
负载电流()式()式解释
大小、极性、联接方式
P253 说明转换后电源正负极性,这里不算。
P303 自己看
b
虚线左侧为电源,右侧为负载
Is
Rin
RL
a
IL
IL
内阻相等,IS*Rin=E时电流源与电压源对负载RL等效。
验证两种情况下IL相等。解释:大小、极性、联接方式
P253 EXAMPLE
a. Convert the current source of Fig to a voltage source, and find the load current for each source.
b. Replace the 6-k load with a 10- load, and calculate the current IL for the current source.
c. Repeat the calculation of part (b) assuming that the current source is ideal (Rs=) because RL is so much smaller than RS. Is this one of those situations where assuming that the source is ideal is an appropriate approximation?
4. 电流源的连接
a. 电流源并联
b. 不同的电流源不能串联