UNIVERSITI MALAYSIA PERLIS Peperiksaan Semester Pertama Sidang Akademik 2013/2014 Januari 2014 EMT 116 - Electronic Devices [Peranti Elektronik] Masa : 3 jam Please make sure that this question paper has FIFTEEN (15) printed pages, including this front page before you start the examination. [Sila pastikan kertas soalan ini mengandungi LIMA BELAS (15) muka surat yang bercetak, termasuk muka hadapan sebelum anda memulakan peperiksaan.] This question paper has SIX (6) questions. Answer any FIVE (5) questions. [Kertas soalan ini mengandungi ENAM (6) soalan. Jawab mana-mana LIMA (5) soalan sahaja.] Appendix A and B are given in this question paper. [Lampiran A dan B diberi dalam kertas soalan ini.]
(EMT 116) -2- Question 1 [Soalan 1] (a) Explain the energy gap of a semiconductor. [Terangkan sela tenaga bagi semikonduktor.] (b) An intrinsic silicon crystal at room temperature has sufficient heat energy for some valence electrons to jump from valence band into the conduction band. Discuss the creation process of electron-hole pair. [Hablur silikon hakiki pada suhu bilik mempunyai tenaga haba yang mencukupi untuk beberapa elektron valensi melompat dari jalur valensi ke dalam jalur konduksi. Bincangkan proses pembentukan pasangan elektron-lubang.] (4 Marks / Markah) (c) Diode is a two terminal semiconductor device which is normally used to develop direct current (DC) power supply. Illustrate a complete block diagram of a DC power supply by showing a corresponding output voltage waveform for each component used. [Diod adalah dua pengkalan peranti semikonduktor yang biasanya digunakan untuk membangunkan bekalan kuasa arus terus (AT). Ilustrasikan satu rajah blok bekalan kuasa AT yang lengkap dengan menunjukkan gelombang voltan keluaran bagi setiap komponen yang digunakan.] (6 Marks / Markah) (d) A center-tapped (CT) rectifier is a type of full-wave rectifier that uses two silicon diode connected to the secondary of a center-tapped transformer as shown in Figure 1.1. [Suatu penerus sadap-tengah (CT) merupakan sejenis penerus gelombang-penuh yang menggunakan dua diod silikon yang disambungkan kepada pengubah sekunder sadap-tengah seperti yang ditunjukkan dalam Rajah 1.1.] (i) Evaluate the peak voltage across each half of the secondary winding. [Nilaikan voltan puncak merentasi setiap bahagian gegelung sekunder.] (ii) Evaluate the peak inverse voltage (PIV) rating for the diodes. [Nilaikan voltan songsang puncak (PIV) kadaran untuk diod-diod tersebut.]. 3/-
(EMT 116) -3- (iii) Evaluate the output load voltage across RL and sketch its waveform. [Nilaikan voltan beban keluaran merentasi R L dan lakarkan gelombang.] (4 Marks / Markah) [Figure 1.1] [Rajah 1.1]
(EMT 116) -4- Question 2 [Soalan 2] (a) Differentiate the following diodes: [Bezakan diod-diod berikut:] (i) (ii) (iii) Varactor [Varactor] Schottky [Schottky] PIN [PIN] (6 Marks / Markah) (b) With the aid of a diagram, sketch and summarize the complete I-V characteristics curve of a Zener diode. [Dengan bantuan gambarajah, lakar dan rumuskan graf lengkung ciri-ciri I-V yang lengkap bagi diod Zener.] (7 Marks / Markah) (c) Figure 2.1 shows a Zener regulator circuit with varying input voltage,vin. By referring to the datasheet in Appendix A, evaluate: [Rajah 2.1 menunjukkan litar pengatur Zener dengan voltan input, V in boleh ubah. Dengan merujuk kepada lampiran Appendix A, nilaikan:] (i) output voltage, Vout at Zener knee current, IZK. [Voltan keluaran, V out pada arus lutut Zener, I ZK.] (ii) output voltage, Vout at Zener maximum current, IZM [Voltan keluaran, V out pada arus maksimum Zener, I ZM.] (iii) minimum and maximum input voltages that can be regulated by the Zener diode. [Voltan minimum dan maksimum yang boleh diatur oleh Zener diod.] (3 Marks /Markah). 5/-
(EMT 116) -5- Figure 2.1 [Rajah 2.1]
(EMT 116) -6- Question 3 [Soalan 3] (a) Differentiate between npn and pnp bipolar junction transistor. [Bezakan antara transistor simpang dwikutub npn dan pnp.] (4 Marks /Markah) (b) Discuss the bias conditions of the base-emitter and base-collector junctions for a transistor to operate as an amplifier. [Bincangkan keadaan-keadaan pincang simpang tapak-pemancar dan simpang tapak-pemungut supaya transistor beroperasi sebagai suatu penguat.] (4 Marks /Markah) (c) Consider the npn transistor circuit as shown in Figure 3.1. The transistor has the following parameters: VBE(on) = 0.7 V and β = 50. [Pertimbangkan suatu litar transistor npn seperti dalam Rajah 3.1. Transistor tersebut mempunyai parameter-parameter seperti berikut: V BE(on) = 0.7 V dan β = 50.] (i) Evaluate the collector-emitter voltage, VCE, the base-emitter voltage, VBE, and the collector-base voltage, VCB. [Nilaikan voltan pemungut-pemancar, V CE, voltan tapak-pemancar, V BE, dan voltan pemungut-tapak, V CB.] (7 Marks /Markah) (ii) Decide whether this transistor is saturated or not. Justify your answer. Assume VCE(sat) = 0.2 V. [Tentukan samada transistor ini telah tepu atau tidak. Justifikasikan jawapan anda. Anggapkan V CE(sat) = 0.2 V.] (5 Marks /Markah). 7/-
(EMT 116) -7- Figure 3.1 [Rajah 3.1]
(EMT 116) -8- Question 4 [Soalan 4] (a) With the aid of diagrams, differentiate linear and non-linear operations of a bipolar junction transistor (BJT) as an amplifier. [Dengan bantuan gambarajah-gambarajah, bandingkan operasi linear dan tidak linear bagi sebuah transistor simpang dwikutub (BJT) sebagai suatu penguat.] (3 Marks / Markah) (b) Based on Figure 4.1, evaluate; [Berdasarkan Rajah 4.1, nilaikan;] (i) collector current at DC operating point (Q-point), ICQ. [arus pemungut di titik operasi AT (titik-q), I CQ] (ii) collector to emitter voltage at DC operating point (Q-point), VCEQ. [voltan pemungut ke tapak di titik operasi AT (titik-q), V CEQ] (3 Marks / Markah) (iii) collector current at saturation, IC(SAT). [arus pemungut ketika tepu, I C(SAT).] (3 Marks / Markah) (iv) collector to emitter voltage at cutoff, VCE(cutoff). [voltan pemungut ke tapak ketika potong,v CE(cutoff).]. 9/-
(EMT 116) -9- Vcc = 15V Rc = 4.7 kω βdc = 200 RB = 47 kω RE = 10 kω Figure 4.1 [Rajah 4.1] VEE = -8V (c) As a product engineer, you are required to design a complete biasing circuit for your amplifier project. Recommend a suitable circuit design with a stable Q-point considering the information in Table 4.1. [sebagai seorang jurutera produk, anda dikehendaki merekabentuk sebuah litar pincangan yang sempurna bagi projek penguat anda. Cadangkan satu litar yang sesuai dengan kestabilan titik-q dan mengambilkira informasi dalam Jadual 4.1.] Table 4.1 [Jadual 4.1] Parameter [Parameter] DC Current Gain, β [Gandaan Arus AT, β] Threshold Voltage, VTH [Voltan Ambang, V TH] Collector Resistance, RC [Rintangan Pemungut, R C] Resistance of R2 [Rintangan di R 2] Collector-Emitter Voltage, VCE [Voltan Pemungut-Pemancar, V CE] Supply Voltage, VCC [Voltan Sumber, V CC] Collector Current, IC [Arus Pemungut, I C] Value [Nilai] 140 2 V 10 kω 3.9 kω 12.34 V 22 V 0.84 ma (7 Marks / Markah)
(EMT 116) -10- Question 5 [Soalan 5] (a) Sketch and label the physical structure of n-channel enhancement mode MOSFET. [Lakar dan labelkan struktur fizikal MOSFET saluran-n mod peningkatan] (5 Marks / Markah) (b) The drain current of a particular n-channel enhancement mode MOSFET is found to be 4 ma when VGS = VDS = 9 V, and 1 ma when VGS = VDS = 5 V. Evaluate the conductivity parameter, K, and the threshold voltage, Vt, for this device. Use MOSFET equation in saturation region. (Note: VGS = gate to source voltage and VDS = drain to source voltage.) [Arus salir sesuatu MOSFET saluran-n mod peningkatan adalah 4 ma apabila V GS = V DS = 9 V, dan 1 ma apabila V GS = V DS = 5 V. Nilaikan parameter keberaliran, K, dan voltan ambang, V t, bagi peranti ini. Gunakan persamaan MOSFET dalam kawasan tepuan. (Nota: V GS = voltan get kepada sumber dan V DS = voltan salir kepada sumber.] (5 Marks / Markah) (c) A voltage-divider bias is used in the circuit as shown in Figure 5.1. The transistor Q1 in this circuit has the following parameters; conductivity, K = 0.25 ma/v 2 and threshold voltage, Vt = 1 V. [Pincangan pembahagi-voltan digunakan di dalam litar seperti yang ditunjukkan pada Rajah 5.1. Transistor Q1 dalam litar ini mempunyai parameter-parameter berikut; keberaliran. K = 0.25 ma/v 2 dan voltan ambang, V t = 1 V.] i) Evaluate the gate voltage, VG of transistor Q1. [Nilaikan voltan get V G bagi transistor Q1.] (4 Marks / Markah) ii) Predict the source resistance, RS and drain resistance, RD so that the drain bias current, ID = 1 ma and the output voltage, VOUT = 5 V. [Ramalkan rintangan punca, R S, dan rintangan salir, R D, supaya arus pincang salir, I D = 1 ma dan voltan keluaran, V OUT = 5 V.] (6 Marks / Markah). 11/-
(EMT 116) -11- Figure 5.1 [Rajah 5.1]
(EMT 116) -12- Question 6 [Soalan 6] (a) Sketch circuit symbols for n-channel and p-channel junction field effect transistor (JFET). [Lakarkan simbol-simbol litar untuk transistor kesan medan simpang (JFET) bagi saluran-n dan saluran-p.] (b) With the aid of a diagram(s), discuss the operation of n-channel JFET. [Dengan bantuan gambarajah, bincangkan operasi JFET bagi saluran-n.] (8 Marks / Markah) (c) The transistor Q2 in the circuit shown in Figure 6.1 is biased with a constantcurrent source, IQ = 0.8 ma. This transistor has the parameters as in Table 6.1. [Transistor Q2 di dalam litar yang ditunjukkan dalam Rajah 6.1 telah dipincang dengan sumber arus-tetap, I Q = 0.8 ma. Transistor ini mempunyai parameter-parameter seperti dalam Jadual 6.1] Table 6.1 [Jadual 6.1] Parameter [Parameter] saturated drain current, IDsat [arus salir tepu, I Dsat ] pinchoff voltage, VP [voltan jepitan,, V P ] early voltage, VA [voltan awalan, V A ] Value [Nilai] 2.5 ma 2.5 V (i) Identify the type of transistor Q2. [Kenalpastikan jenis transistor Q2.] (1 Mark /Markah). 13/-
(EMT 116) -13- (ii) Assuming that the transistor Q2 is biased in the saturation region, evaluate drain voltage, VD and source voltage, VS of the circuit in Figure 6.1. [Dengan beranggapan transistor Q2 dipincang dalam kawasan tepu, nilaikan voltan salir, V D dan voltan punca, V S bagi litar dalam Rajah 6.1.] (9 Marks /Markah) Figure 6.1 [Rajah 6.1] -ooooo-
(EMT 116) -14- Appendix A [Lampiran A] Zener Diode Datasheet
(EMT 116) -15- Appendix B [Lampiran B] 1. MOSFET equation: I DSat K V V 2 GS t 2. JFET equation: 2 V GS V I D I DSat 1 1 V P V DS A