华南理工大学《电工学》考试真题1.docx

华南理工大学期末考试

《电路与电子技术》（双语）试卷A

考试时间：120 minutes

注意事项：1.考前请将密封线内填写清楚；

2. 所有答案请直接答在答题纸上； 3. 考试形式：闭卷；

4. 本试卷共 八 大题，满分100分，考试时间120分钟。

Date： Janu ary, 1 8 , 2 0 0 8

题号 得分 评卷 人 I II III IV V VI VII VIII 总分 I. Select the correct answers for the following problems

选择题(每小题3分，共30分)

1. When Fig. 1 is converted into Fig. 2, and I2 will ( • (a)increase (b)not change (c)decrease

)。

2

Fig 1

Fig. 2

2. In Fig. 2, S is on when r=0, if uc (0_ ) = 0 V , then UL (0+ )=( (a)-l()V

(b)10V

(c)0V

lkQ 1 H

)。

｛聲

Fig .2 RLC circuit

3. Assume the rms value of a sinusoidal voltage u is 220V, frequency is 50Hz, when r=0, M(0)=220V, the formula of the sinusoidal voltage is ( (a)u=380sin 1 00K/V

(b)w=311 sin(l 00皿+45°) V

(c)w=220sin(100nr+90°)V

)o

4. Small signal equivalent circuit can be used for ( (a) (b)

dynamic analysis of a transistor amplifier Q-point calculation of a transistor amplifier

)•

(c ) dynamic analysis and Q-point calculation of a transistor amplifier

5. As shown in Fig.3, the two ideal diodes arc of the same type, w =3sin69ZV, M =3V, R=4kG, A then voltage up equal ( (a) 3V

).

(b) 3sincotV

(c) 3V+3s加初 V

ri

6. In the following circuit, the MOSFET

has Vto=lV,九=0, K=0.25mA/V, ID is (). (a) 1mA (b) 0.563mA (c) 0.5mA

410V

OK Fig. 5 A Common-Source Amplifier

7. Fig. 5 shows a BJT amplifier, BJT works in ( (a)active region

(b)saturation region

)。

(c)cutoff region

8. In Fig. 6, Assume R\\ = \\0kfl, /?2= 100kfl, if UQ=6V，then )°

wj=( (a)6V(b)3 V(c)6/11 V(d)3/11V

Fig. 6 A operational amplifier circuit

9. Fig. 7 shows a rectify circuit, the average output voltage 6 () is 18V, if one of diodes is damaged and cutoff, then the average output voltage U° is (a)10V)°

(b)20V

Fig. 7 a DC voltage source

10. Logic circuit and the curve of A and B are shown in Fig.8t F is (a)

when t is (

).

II. (10 scores) The circuit is shown in Fig.9, assume C/S2=0.2V, /S=1A, /?]=/?5=/?6=/?7=lQ,

/?2=/?3=2G, /?4=5Q> if 1=09 determine (7S1=? With Thevenin^s Law

A

B

III. (10 scores) When Z=0, the S is off z=0, assume /?!=60kQ, /?2=40k Q, /?3=6kQ, C=5pF,

Fig. 10

IV. (12 scores) In Fig. 11, 2=6.6kvaro Find (1)

w = 220V2sin314/V, apparent power P=8.8kW, reactive power

I(R,

i which flows through R and L, uL and PF (2)plot phasor graphy of

+

R MR

V. (10 scores) In Fig. 12, write the formula between w0 and wj\\, u[2 •

Fig」2 A Complex Op Circuit

VI. (10 scores)

In the following figure, u2 = 20^2 sirBld N , C = 500/zF, R、= 500, Find： (l)When S is off,

the average voltage 〃° = ? the maximum reverse voltage of DI and D2 the average voltage 〃()= ? The average current flows through DI and D2

〃阴=?

⑵ When S is on,

侶？

0 Ar

Fig. 13 Recitify Circuit

VII. (12 scores)

Assume Ucc =12V,/?BI =7.5 lil,/?B2 = 2.5 Ifl,7?c = 2 in ,/?E = 1 1G, /?=50,t/BE =0.7 V, determine (1) Q-point； (2) small signal equivalent circuit；

Fig・ 14 A Common-Emitter Amplifier

VIII. (8 scores) In Fig」5, detennine two logic formula.

Fig-15 Two Complex Logic Circuit