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Name:
Matric No:
Section:
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
MID TERM EXAMINATION
SEMESTER II, 2014/2015 SESSION
KULLIYYAH OF ENGINEERING
Program
Time
Duration
Section(s)
Course Title
: ENGINEERING
: 10.00 am – 12.00 pm
: 2 hours
: 1-9
: Electronics
Level of Study
Date
Course Code
: UG1
: 04/04/2015
: ECE 1312
This Question Paper Consists of Nine (10) Printed Pages Including Cover Page With four (4)
Questions.
INSTRUCTION(S) TO CANDIDATES
DO NOT OPEN UNTIL YOU ARE ASKED TO DO SO



Total marks of this examination is 60.
This examination is worth 25% of the total assessment
Answer all 4 (FOUR) questions.
Any form of cheating or attempt to cheat is a serious offence which may lead to
dismissal.
1
Question 1 [15 marks]
a) The bandgap energy of semiconductor "X" is 1.1 eV and the bandgap energy of
semiconductor "Y" is 2.1 eV. Which semiconductor material has less temperature effect
on its current (is it semiconductor X or Y)? Explain why.
(4 marks)
b) Calculate the majority and minority charge carrier concentrations in Silicon at
T = 300 K. Assume, for Silicon ni = 1.5×1010 cm-3.
(6 marks)
(i) Na = 1017 cm-3
(ii) Nd = 5×1015 cm-3
2
c) Consider a p-n junction is formed by using the material as mentioned in question 1(a).
Calculate the built in potential of the p-n junction.
(3 marks)
d) How can diodes be damaged in a working electronic circuit?
(2 marks)
3
Question 2[15 marks]
a) A diode circuit is shown in Fig. 2(a). Assume that the circuit and diode parameters
are 𝑉𝐷𝐶 = 10 𝑉, 𝑅 = 5.0 𝑘Ω, 𝑉γ = 0.6 𝑉, 𝑉T = 0.026 𝑉 and 𝑣𝑎𝑐 = 0.2 sin 𝜔𝑡 (𝑉).
(8 marks)
(i) Perform DC analysis and calculate VO and ID.
(ii) Using AC analysis, calculate the diode’s resistance rd, AC voltage, vo and AC
current, id
Fig. 2(a)
4
b) Figure 2(b) shows a center tapped full-wave rectifier circuit. Consider the primary voltage
source 𝑣𝑝 = 120 sin 𝜔𝑡 (𝑉) and the transformer turns ratio is 8:1.
(7 marks)
(i) Determine the value of resistance R such that the peak current is 95.33 mA.
(ii) Find the peak inverse voltage (PIV) of each diode.
Fig. 2(b)
5
Question 3 [15 marks]
a) Consider the Zener diode circuit as shown in Fig. 3(a). Assume that the Zener diode and
circuit parameters are, 𝑉𝑍 = 5.6 𝑉 and 𝑅𝑖 = 50 𝛺. Determine the values of 𝐼𝑍, 𝐼𝐿 , and 𝑉𝐿,
for the following conditions:
(8 marks)
(i) 𝑉𝑃𝑆 = 10 𝑉, 𝑅𝐿 = ∞
(ii) 𝑉𝑃𝑆 = 15 𝑉, 𝑅𝐿 = 250𝛺
Fig. 3(a)
6
b) Consider the circuit is as shown in Fig. 3(b). The diode cut-in voltage is 𝑉𝛾 = 0.7 𝑉.
Calculate the output voltage 𝑣𝑂 and plot it with respect to the input voltage 𝑣𝐼 in the same
time scale over the range of voltages −10 𝑉 ≤ 𝑣𝐼 ≤ +10 𝑉 for 𝑉𝐵 = 5𝑉.
(3 marks)
Fig. 3(b)
7
c) A diode circuit is as shown in Fig. 3(c). Assume circuit parameters are 𝑅1 = 3 𝑘𝛺,
𝑅2 = 1 𝑘𝛺, 𝑉𝛾 = 0.7 𝑉, 𝑉 + = +6 𝑉 and 𝑉 − = −5𝑉. Determine the values of 𝑣0, and 𝑖𝐷1 .
(4 marks)
Fig. 3(c)
8
Question 4 [15 marks]
(a) A common emitter BJT circuit is designed as shown in Fig. 4(a). The output load line and
defined Q-point of the circuit are shown in Fig. 4(a). Determine the required values of 𝑉CC , 𝑅C
and 𝑅B . Assume that 𝑉BE (on) = 0.7 V.
(6 marks)
Fig. 4(a)
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(b) Prove that,  

 1
(3 marks)
(c) For the transistor circuit shown in Fig. 4(c), assume VBE(on) = 0.7V and β = 100. Find the
values of IBQ, ICQ, IEQ and VCEQ.
(6 marks)
Fig. 4(c)
10