* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Questions
Nanofluidic circuitry wikipedia , lookup
Integrated circuit wikipedia , lookup
Integrating ADC wikipedia , lookup
Wien bridge oscillator wikipedia , lookup
Index of electronics articles wikipedia , lookup
Josephson voltage standard wikipedia , lookup
Power electronics wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Transistor–transistor logic wikipedia , lookup
Regenerative circuit wikipedia , lookup
RLC circuit wikipedia , lookup
History of the transistor wikipedia , lookup
Surge protector wikipedia , lookup
Wilson current mirror wikipedia , lookup
Voltage regulator wikipedia , lookup
Schmitt trigger wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Current source wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Operational amplifier wikipedia , lookup
Power MOSFET wikipedia , lookup
Two-port network wikipedia , lookup
Rectiverter wikipedia , lookup
Opto-isolator wikipedia , lookup
K U L L I Y Y AH O F E N G I N E E R I N G END-OF-SEMESTER EXAMINATION SEMESTER 1, 2015/2016 SESSION Programme : Engineering Level of Study : UG 1 Time : 9.00 am -12.00 pm Date : 03/01/2016 Duration : 3 Hrs Course Code : ECE 1312/EECE 1312 Section(s) : 1- 5 Course Title : Electronics This Question Paper Consists of 12 (Twelve) Printed Pages (Including Cover Page) with 5 (Five) 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 course assessment. Answer ALL QUESTIONS Only approved calculator with ‘KoE approved’ sticker is allowed (non-programmable and non-graphical). Marks assigned to each problem are listed in the margins. Any forms of cheating or attempt to cheat is a serious offence which may lead to dismissal. All electronics gadgets are prohibited in the exam hall / venue. (e.g. mobile / smart phones, smart watches, and smart glasses) APPROVED BY: 1 QUESTION 1 (20 marks) a) A solar cell is a special type of pn-junction diode. The current equation of a particular solar cell is represented as follows: 𝐼𝐷 = 5.0 × 10 −13 [𝑒 𝑉 ( 𝐷) 𝑉𝑇 − 1] − 7.7 × 10−2 (A) When the cell is irradiated with sunlight and the cell current, 𝐼𝐷 = 0, the voltage 𝑉𝐷 is referred to as the open circuit voltage, 𝑉𝑂𝐶 . Similarly, when the cell is irradiated in the sunlight and the cell voltage, 𝑉𝐷 = 0, the current 𝐼𝐷 at that time is called the short circuit current, 𝐼𝑆𝐶 . If the cell is operating at room temperature determine the parameters of the solar cell as follows: (4 + 2 marks) i. Open circuit voltage, 𝑉𝑂𝐶 ii. Short circuit current, 𝐼𝑆𝐶 b) Consider the circuit shown in Fig. 1(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 = 5 V. (4 marks) Fig. 1(b) 2 c) A clamper circuit is shown in Fig. 1(c). Write the equation of input-output voltage relation of the circuit. Sketch the output voltage waveform, 𝑣𝑂 against the time, t, if the input has sinusoidal voltage, 𝑣𝐼 = 6 sin(𝜔𝑡) V and diode cut-in voltage, 𝑉𝛾 = 0 V. (4 marks) Fig. 1(c) d) In the circuit shown in Fig. 1(d), the power rating of the Zener diode is 4 W. Let, 𝑉𝐼 = 58 𝑉, 𝑅𝑖 = 150 𝛺, 𝑉𝑍 = 16 V and the minimum diode current is 15 mA. (2 + 4 marks) i. Determine the range of the diode current ii. Determine the range of the load resistance, 𝑅𝐿 Fig. 1(d) 3 QUESTION 2 (20 marks) a) Consider the circuit shown in Fig. 2(a). Assume that 𝑉𝐶𝐶 = 2.8 V, 𝛽 = 180 and 𝑉𝐵𝐸 (on) = 0.7 V. Design the circuit by finding the values of 𝑅𝐵 and 𝑅𝐶 such that 𝐼𝐶 = 0.12 mA and 𝑉𝐶𝐸 = 1.4 V. (6 marks) Fig. 2(a) b) A transistor has current gain, 𝛽 in the range of 90 ≤ 𝛽 ≤ 180 and the collector current, 𝐼𝐶 is in the range of 0.8 mA ≤ 𝐼𝐶 ≤ 1.2 mA. What is the possible range of 𝑔𝑚 and 𝑟𝜋 ? Assume that 𝑉𝑇 = 0.026 V. (5 marks) 4 c) A common collector circuit is shown in Fig. 2(c). Given that = 100. Assume 𝑉𝐵𝐸 (on) = 0.7 V. (3 + 3 + 3 marks) i. Calculate the value of the DC collector current 𝐼𝐶 ii. Sketch the small signal AC equivalent circuit. Assume that 𝑉𝐴 = ∞ iii. Calculate the value of the output resistance 𝑅𝑂 Fig. 2(c) 5 QUESTION 3 (20 marks) a) A transistor transconductance, 𝑔𝑚 = 50 mA/V and emitter resistance 𝑟𝜋 = 1.5 kΩ when it is operating at room temperature. Determine the collector current 𝐼𝐶𝑄 and common emitter-current gain 𝛽 of the transistor. Assume that 𝑉𝑇 = 0.026 V. (4 marks) b) A common-emitter amplifier has output voltage −2.4 V when its input voltage is 250 mV. The collector resistance of the amplifier has 1.5 kΩ is changed to 2.5 kΩ, what is the new voltage gain of the amplifier ? Consider that 𝑟𝑂 = ∞. (5 marks) c) For the common emitter circuit in Fig. 3(c), the transistor parameters are 𝛽 = 100 and 𝑉𝐴 = ∞. The parameters of the circuit are 𝑉𝐵𝐸 (on) = 0.7 V, 𝐼𝐶 = 0.5 mA and 𝑉𝐶𝐸 = 3 V. (5 + 2 + 4 marks) i. Find the value of 𝑅𝐸 and 𝑅𝐶 ii. Draw the small-signal equivalent circuit iii. Determine the value of the voltage gain, 𝐴𝑣 = 𝑣𝑂 /𝑣𝑆 6 Fig. 3(c) 7 QUESTION 4 (20 marks) a) The transistor in the circuit in Fig. 4(a) has parameters 𝑉𝑇𝑁 = 0.8 V and 𝐾𝑛 = 0.2 mA/V 2 . Sketch the output load line and plot the Q-points for 𝑉𝐷𝐷 = 2 V and 𝑅𝐷 = 2 kΩ. Assume the transistor is biased under saturation mode. (7 marks) Fig. 4(a) b) The transistor in Fig. 4(c) has parameters 𝑉𝑇𝑁 = 0.4 V, and 𝐾𝑛 = 4.8 mA/V 2 . The parameters of the circuit are 𝐼𝐷 = 0.8 mA and 𝑅1 ||𝑅2 = 200 kΩ . Assume that the transistor is biased under saturation mode. (6 + 3 marks) i. Design the circuit by calculating 𝑅1 and 𝑅2 ii. Calculate the value of 𝑉𝐷𝑆 and confirm that the transistor is biased under saturation mode Fig. 4(c) 8 c) For an NMOS biased in the saturation region, the parameters are 𝐾𝑛′ = 0.1 mA/V 2 , 𝑉𝑇𝑁 = 1.2 V and 𝐼𝐷 = 0.8 mA. Determine the transistor width to length ratio (𝑊/𝐿) such that 𝑔𝑚 = 1.8 mA/V. (4 marks) 9 QUESTION 5 (20 marks) a) The parameters of the common source circuit shown in Fig. 5(a) are 𝑉𝐷𝐷 = 12, 𝑅𝐷 = 3 kΩ, 𝑅𝑆 = 0.5 kΩ, 𝑅1 = 894 kΩ, 𝑅2 = 347 kΩ and 𝑅𝐿 = 10 kΩ . The transistor parameters are, 𝑉𝑇𝑁 = 1.2 V, 𝐾𝑛 = 1.5 mA/V 2 and 𝜆 = 0. (6 + 5 marks) i. Find the values of 𝐼𝐷 and 𝑉𝐷𝑆 ii. Determine the input resistance, 𝑅𝑖𝑛 and the small-signal voltage gain, 𝐴𝑣 Fig. 5(a) 10 b) Determine the output voltage 𝑣𝑂 for 𝑣𝐼 = 3 V for the op-amp circuit shown in Fig. 5(b). Then, calculate the output current that flows through 5 kΩ resistor. (4 marks) Fig. 5(b) c) For the inverting summing amplifier shown in Fig. 5(c), determine the value of 𝑅3 if all the circuit parameters are given as: 𝑅1 = 50 kΩ, 𝑅2 = 40 kΩ, 𝑅𝐹 = 50 kΩ and 𝑣𝑂 = − 10 𝑉. The inputs to the circuit are, 𝑣𝐼1 = 1 V, 𝑣𝐼2 = 2 V and 𝑣𝐼3 = 0.3 V. (5 marks) Fig. 5(c) 11 Some Useful Equations Equation for pn- junction: I D I s (e vD VT 1) Equations for BJT I CQ gm r VT VT I CQ g m r ro VA I CQ Equations for MOSFET I D K n [2VGS VTN VDS VDS ] 2 I D K n VGS VTN 2 𝐾𝑛 = ′ 𝑊 𝑘𝑛 2 𝐿 ro VA 1 I DQ I DQ 1 VA g m 2 K n I DQ END OF PAPER 12