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INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

END OF SEMESTER EXAMINATIONSEMESTER I, 2005/2006 SESSION

KULLIYY H OF ENGINEERING

Programme : ENGINEERING Level of Study : UG 1

Time : 9:00 am- 11:30 am Date : 24/10/2005

Duration : 2 hours 30 minutes

Course Code : ECE 1231 Section(s) : 1, 2 and 3

Course Title : Electronics

This Question Paper Consists of Three (3) Printed Pages (Including Cover Page) WithFive (5) Questions.

INSTRUCTION(S) TO CANDIDATES

DO NOT OPEN UNTIL YOU ARE ASKED TO DO SO

Total mark of this examination is 50 . This examination is worth 50% of the total assessment. Answer all 5 (Five) questions.

Any form of cheating or attempt to cheat is a seriousoffence which may lead to dismissal.

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Electronics ECE 1231

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Q.1 [10 marks](a) Draw a circuit diagram of the noninverting-amplifier and give an expression for the

voltage gain in terms of the resistances, assuming an ideal op-amp. Giveexpressions for the input and output impedances of the amplifier. (6 marks)

(b) Find the output voltage in terms of the input voltages and resistor values for thecircuit shown in Fig. 1 , using the ideal op-amp assumption. What is the inputresistance seen by v A? What is the output resistance seen by R L? (4 marks)

Fig. 1

Q.2 [10 marks](a) Explain that the semiconductor material has a negative temperature coefficient of

resistance. Define the terms of intrinsic and extrinsic semiconductors. Describe thedifference between n-type and p-type semiconductor materials . (5 marks)

(b) Draw an appropriate diode circuit for each of the following: AND gate, OR gate and

voltage doubler. If V SS = 2 V, R = 1 k in the circuit of Fig. 2 , draw the load line ofthe circuit and mark the end values on it. (5 marks)

Fig. 2 Fig. 3

Q.3 [10 marks]The following values are given as design data for the amplifier shown in Fig. 3 :VCC = 12V, V BB = 5V, I CQ = 15.5 mA, V CEQ = 5.8 V, and I BQ = 100A.

(a) Calculate the values of R B and R C. (2 marks) (b) Draw characteristics and mark the Q-point and the dc load line. (4 marks)(c) If the ac input current is 50sin t A, what is the maximum peak ac value of

the undistorted collector-emitter voltage? (4 marks)

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Q.4 [10 marks]Show that the circuit of Fig. 4(b) is more stable than that of Fig. 4(a) by comparing thevalues of I B, IC and V CE, where changes from 50 to 100. (10 marks)

Fig. 4(a) Fig. 4(b)

Q.5 [10 marks](a) The NMOS in Fig. 5 has V to = 1 V, K = 0.25 mA/V 2, = 0. Determine the Q-point

values (V GSQ , IDQ and V DSQ ) of the given circuit. (5 marks)

(b) Draw the small signal mid-frequency ac equivalent circuit and find the inputimpedance Z i, output impedance Z o and voltage gain A v for the given amplifier.

(Assume g m = 1.77 mS and r d = ) (5 marks)

Fig. 5

100

C1

4.7 k

2.7 k

3 M

1 M

C2

C3

R

R 1

R 2

R D

R S

R L

+

vin

+

vo vs 10 k

+20 V

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