Final Exam ECE 1312 Question Sem-2 2013-2014

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

END OF SEMESTER EXAMINATIONSEMESTER II, 2013/2014 SESSION

KULLIYYAH OF ENGINEERING

Programme : ENGINEERING Level of Study : UG 1

Time : 9:00 am- 12:00 pm Date : 29/05/14

Duration : 3 Hours

Course Code : ECE 1312 Section(s) : 1-9

Course Title : Electronics

This Question Paper Consists of Eight (8) Printed Pages (Including Cover Page) With Five (5) 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 50% of the total assessment. Answer ALL FIVE questions.

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

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Electronics ECE 1312 / ECE 1231

Q.1 [20 marks]

a) The voltage regulator circuit as shown in Fig.1(a) is used to power a car radio at VL = 9V from an automobile battery VPS = 13.6V and the current in the radio is 100mA. Assume that I Z=5mA. (12 marks)

i. In which region that the Zener diode is operating. ii. Determine the value of Ri.

iii. Find the power dissipated in the Zener diode.

Fig. 1(a)

b) Calculate the transformer turns ratio of the rectifier circuit as shown in Fig. 1(b) and determine the peak inverse voltage (PIV) of each diode. Assume that the input voltage of the transformer is 220 V(rms), 50 Hz from an AC main line source, the desired peak output voltage of the circuit is 9V and the diode cut-in voltage V = 0.6 V. (8 marks)

Fig. 1(b)

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Q.2 [20 marks]

a) For a BJT circuit and its corresponding output load line shown in Fig. 2(a1) and Fig. 2(a2) respectively. Find the values of RE and RB given that IB = 0.04 mA and = 120. Assume VBE(on) = 0.7 V. (10 marks)

Fig. 2(a1) Fig. 2(a2)

b) A BJT circuit is shown in Fig. 2(b). Determine the values of IC and VEC. Assume = 100 and VEB(on) = 0.7 V. (4 marks)

Fig. 2(b)

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c) Calculate IC and VCE given that = 50 and VBE(on) = 0. 7 V for the circuit as shown in Fig. 2(c). (6 marks)

Fig. 2(c)

Q.3 [20 marks]

a) A transistor has current gain, in the range of 90 180 and the collector current, IC is in the range 0.8 IC 1.2 (mA). What is the possible range in the small signal parameters gm and r ? Assume that VT = 0.026 V. (4 marks)

b) Assume that = 100 and VA = for the common emitter circuit configuration as shown in Fig. 3(b).

i. Calculate the DC collector current. (4 marks)ii. Draw the small-signal equivalent circuit. (2 marks)

iii. Determine the voltage gain, AV. (4 marks)

Fig. 3(b)

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c) A common collector circuit is as shown in Fig. 3(c). Assume that VBE(on) = 0.7 V, β = 100, VT = 0.026 V and VA = 80 V. (6 marks)

i. Calculate the DC collector current.ii. Draw the small signal equivalent circuit together with its AC parameters.

Fig. 3(c)

Q.4 [20 marks]

a) Calculate the current in an NMOSFET. Consider an n-channel enhancement-mode MOSFET with the following parameters: V TN = 0.4 V, W = 50 μm, L= 2 μm, μn= 650 cm2/V-s and Cox = 0.138 × 10-6 F/cm. Determine the current when the MOSFET is biased in the saturation region for vGS=¿2.2 V. (4 marks)

b) Give two differences between Bipolar Junction Transistor (BJT) and Metal Oxide Semiconductor Field Effect Transistor (MOSFET). (4 marks)

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c) Draw the small-signal equivalent circuit of the Fig. 4(c) and determine the small-signal voltage gain, input and output resistance of a common-source amplifier. The circuit parameters are: VDD = 4.5 V, RD = 4.7 kΩ, R1 = 120 kΩ, R2 = 47 kΩ and RSi = 4 kΩ. The NMOS transistor parameters are: VTN = 0.4 V, Kn = 0.6 mA/V2 and λ = 0V −1. (12 marks)

Fig. 4(c)

Q.5 [20 marks]

a) An NMOSFET common-source amplifier circuit with a source resistance is shown in Fig. 5(a). The transistor parameters are, V TN=0.6 V , Kn = 0.2 mA/V2, and λ=0.0083 V−1 (10 marks)

i. Determine the quiescent values of I DQ, V GSQ and V DS Q

ii. Draw the small-signal equivalent circuit and determine the voltage gain Av.

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Fig. 5 (a)

b) Calculate the voltage gain and output voltage VO of the operational amplifier circuit as shown in Fig. 5(b). (5 marks)

Fig. 5 (b)

c) The output voltage of the non inverting op-amp circuit as shown in Fig. 5(c) is 9.5V. Determine the value of resistance R1 of the circuit. (5 marks)

Fig. 5 (c)

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Some Useful Equations

For pn-junction diode:

For BJT:

For NMOSFET:

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I D=I s(e

v D

V T −1)

gm=I CQ

V T

r π=β V T

I CQ

ro=V A

I CQ

I D=Kn [2 (V GS−V TN ) V DS−VDS2 ]

I D=Kn (V GS−V TN )2

ro=1

I DQ λ

gm=2√ Kn I DQ

Kn=Wμn Cox

2 L

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Final Exam ECE 1312 Question Sem-2 2013-2014