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Name: Matric No: Section: INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA MID TERM EXAMINATION SEMESTER I, 2014/2015 SESSION KULLIYYAH OF ENGINEERING Program Time Duration Section(s) Course Title : ENGINEERING : 11.00 am β 13.00 pm : 2 hours : 1-9 : Electronics Level of Study Date Course Code : UG1 : 4/11/2014 : ECE 1312 This Question Paper Consists of Eight (8) Printed Pages Including Cover Page With Five (5) Questions. ο· ο· ο· 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 25% of the total assessment Answer all 5 (Five) questions. Any form of cheating or attempt to cheat is a serious offence which may lead to dismissal. Question 1 a) What are active and passive devices? Give an example for each of them. (4 marks) b) Fig. 1(b) shows a voltage amplifier circuit. The amplifier input resistance, output resistance and open circuit voltage gains are π π = 2.5 kΞ©, π 0 = 200 Ξ© and π΄0 =150 respectively. A voltage source with resistances π π = 1.5 kΞ© and a load resistance of π πΏ = 500Ξ© are connected to the amplifier as shown in Fig. 1(b). (6 marks) i. Find the value of vi in terms of vs ii. Find the value of vo in terms of vs iii. Deduce the value of the actual voltage gain, π΄π£ = Fig. 1(b) π£π π£π of the amplifier Question 2 a) How to make a p-type and a n-type extrinsic semiconductors? ( 4 marks) b) At 30o C temperature with thermal equilibrium condition, the minority charge carrier (electron) concentration of a p-type silicon material is 2.5×105 cm-3. Determine the acceptor atom concentration of the material. (Boltzmannβs constant π = 86 × 10β6 ππ/πΎ). (Please refer to the table on the last page) ( 6 marks) Question 3. As shown in Fig. 3, a Silicon pn-junction diode is working at a temperature 350° K. The diode has been constructed with doped at 1.2 × 1016 cm-3 in p-type and 1.0 × 1017 cm-3 in n-type semiconductors. Determine the diode current πΌπ· in the circuit by using the diode constant voltage model where Vο§ equals to the built-in potential voltage of the diode, Vbi (Please refer to the table on the last page) (10 Marks) Fig. 3 Question 4. a) State two differences between the center-tapping full- wave rectifier and bridge rectifier circuits. ( 4 marks) b) Design a full-wave bridge rectifier circuit for a desired peak output current, πΌπΏ = 150 mA with a transformer feed as shown in Fig. 4(b). Assume that the transformer primary is connected with a 220 V(rms) main supply line and the circuit diode cut-in voltage VΞ³ = 0.65 V. (Hints, determine the transformer turns ratio). ( 6 marks) Fig. 4(b) Question 5 a) Design a Zener diode voltage regulator circuit as shown in Fig. 5(a). Consider the Zener breakdown voltage and current are, ππ = 8.5 π and πΌπ = 35 ππ΄ respectively. ( 6 marks) Fig. 5(a) b) A diode clipper circuit as shown in Fig. 5(b). Its input voltage π£πΌ is a 20 VPP triangular waveform. Sketch the output waveform π£π of the clipper circuit on the graph is given at the right side of the circuit. Assume that ππ΅ = 3 π and ππΎ = 0.65 π. ( 4 marks) Fig. 5(b) Semiconductor Constants Material Bandgap Energy (eV) B (cm-3 K-3/2) Silicon 1.1 5.23 × 1015 Germanium 0.66 1.66 × 1015 Gallium Arsenide 1.4 2.10 × 1014