Name: Matric No:

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

MID TERM EXAMINATION

SEMESTER 2, 2010/2011 SESSION

KULLIYYAH OF ENGINEERINGKULLIYYAH OF ENGINEERINGKULLIYYAH OF ENGINEERINGKULLIYYAH OF ENGINEERING

Program : ENGINEERING Level of Study : UG1

Time : 10 am – 12:00 pm Date : 12/2/2011

Duration : 2 hours

Course Code : ECE 1312 Section(s) : 1-10

Course Title : Electronics

This Question Paper Consist of Four (5) Printed Pages (Including Cover Page) With Four (4)

Questions.

INSTRUCTION(S) TO CANDIDATES

DO NOT OPEN UNTIL YOU ARE ASKED TO DO SO

● Total mark of this examination is 100

● This examination is worth 15% of the total final assessment.

● Answer all 4 (Four) questions.

Any form of cheating or attempt to cheat is a serious offence which may lead to

dismissal.

Electronics ECE 1312

Q.1 [20 marks]

a) Silicon with an intrinsic carrier concentration of 1.5 x 1010

/cm3 is doped with 5 x 10

16

atoms/cm3

of an element X. After doping, silicon becomes an n-type material.

(10 marks)

i) Give an example of element X.

ii) Calculate the electron and hole concentrations in the material at T= 300K.

Electronics ECE 1312

iii) Consider a p-n junction with the n-type doping the same as above, 5 x 1016

atoms/cm3. If the built in voltage is to be 0.712 V , what is the p-type doping

concentration?

b) Describe the difference between drift and diffusion currents and state their governing

equations (5 marks)

Electronics

c) For the circuits shown in

voltage V.

shown in Fig. 1(c), assume that Vγ = 0.7 V. Calculate the current I and

Fig. 1(c)

ECE 1312

V. Calculate the current I and

(5 marks)

Electronics

Q.2 [20 marks]

a) The full wave rectifier circuit shown in

50 Hz. The rms value of υ

i. What is the maximum value of

ii. What is the Peak Inverse Voltage (PIV) rating of each diode?

The full wave rectifier circuit shown in Fig. 2(a) has an input signal whose frequency is

50 Hz. The rms value of υs = 8.5 V Assume each diode cut-in voltage is V

What is the maximum value of vo?

nverse Voltage (PIV) rating of each diode?

Fig.2(a)

ECE 1312

has an input signal whose frequency is

in voltage is Vɤ = 0.7 V.

(5 marks)

Electronics

b) The diode circuit shown in

Plot the Vo against time. As

Fig. 2(b)(i)

-5 V

15

V

he diode circuit shown in Fig. 2(b)(ii) has a square wave input shown in

Assume a cut-in voltage, Vγ = 0.6 V and VB = 5 V.

(i) Fig. 2(b)(ii)

ECE 1312

has a square wave input shown in Fig. 2(b)(i).

= 5 V. (5 marks)

Electronics ECE 1312

c) The clamper circuit shown in Fig. 2(c)(i) has a sinusoidal wave input shown in Fig.

2(b)(ii) with VM = 5 V. Plot the Vo against time. Assume a cut-in voltage, Vγ = 0.7 V.

(5 marks)

Fig. 2(c)(i) Fig. 2(c)(ii)

Electronics ECE 1312

d) A Zener diode circuit is shown in Fig. 2(d). Calculate RL such that IZ = 0.1 IR. (5 marks)

Fig. 2(d)

IR IRL

Electronics ECE 1312

Q.3 [20 marks]

a) The npn transistor shown in Fig. 3(a) has a current source, IE = 1.5 mA and β = 100.

Determine IB, IC, α and VC. What mode is the transistor operating in? (5 marks)

Fig. 3(a)

Electronics ECE 1312

b) The pnp transistor shown in Fig. 3(b) has β = 100. Plot the voltage transfer characteristic

(VO versus VI) over the range 0 ≤ VI ≤ 5 V. (7 marks)

Fig. 3(b)

Electronics ECE 1312

c) The pnp transistor shown in Fig. 3(c) is operating in saturation with VEC (sat) = 0.2 V and

VEB = 0.7V. Calculate IB, IC, IE and β. Sketch the load line and plot the Q-point values for

the IC versus VEC graph. (8 marks)

Fig. 3(c)