Menoufia National University Electronic Circuits and Devices Midterm Exam PDF

Menoufia National University Faculty of Applied Health Sciences Technology Midterm exam Academic Year: 2023/2024 Date: 26/03/2023 Program: General program Time: 60 Mins. Level: 0...

Menoufia National University Faculty of Applied Health Sciences Technology Midterm exam Academic Year: 2023/2024 Date: 26/03/2023 Program: General program Time: 60 Mins. Level: 0 No of exam pages: 4 Course Title: Electronic circuits and devices No of questions: 2 Course Code: OFRE 111 Total marks: 20 Midterm exam Answer the following questions: Question 1 Decide which of these statements are true or false. 1) In N-type material, electrons are the majority carriers and holes are the minority carriers. 2) The constant drop model of a diode works as a switch (forward is short circuit and reverse is open circuit) 3) The full wave rectifier using bridge is preferred because we use only two diodes. 4) In the forward biased case, the current pass through the PN junction form cathode to anode. 5) The reverse biased case for the diode is achieved by applying positive charge to anode and negative charge to cathode. 6) The average voltage of the half wave rectifier is greater than that of the full wave rectifier. 7) Donors materials have atoms with five valence electrons and are used to make P type material. 8) The pure semiconductor materials have higher conductivity than N- and P-type semiconductor materials. 9) In the forward biased ideal model, the diode is short circuit, but in the reverse biased the diode acts as open circuit. 10) A rectifier is a device that converts the alternating current (AC) to direct current (DC). 11) For the same input voltage, the peak inverse voltages (PIV) of the center-tapped transformer full wave rectifier is greater than that of the half wave rectifier. Page 1 of 4  12) In semiconductor materials, the current which flows due to electric field is called the diffusion current. 13) The concentration 𝒏 of electrons in p-type semiconductor is calculated from 𝒏𝟐𝒊 𝒏= 𝑵𝑨 14) The doping process for pure semiconductors is achieved using acceptors or donors atoms. 15) In the full wave rectifier, the center tapped transformer is used to set up the input voltage. 16) To buy a diode, we must buy the diode with break down voltage equals the peak inverse voltage. 17) In semiconductor materials, charge carriers are electrons and holes. 18) Acceptor materials have atoms with three valence electrons and are used to make P type material. 19) Semiconductor materials have a negative temperature coefficient: as the temperature rises, their resistance decreases. 20) The diode is made from two PN junctions. Question 2 Choose the correct answer 21. The average voltage of a full wave rectified voltage with a peak value of 300 V is a. 300/𝝅 b. 300 c. 600/ 𝝅 d. 95.5 22. When the peak output voltage is 100 V, the PIV for each diode in a center-tapped full wave rectifier is (the diode model is constant drop voltage) a. 100 b. 199.3 c. 200 d. 50 23. the concentration 𝑷 of holes in 𝒏-type semiconductor is a. 𝒏𝟐𝒊 b. 𝒏𝟐𝒊 𝑷= 𝑷= 𝑵𝑫 𝑵𝑨 c. 𝒏𝒊 d. 𝒏𝒊 𝑷= 𝑷= 𝑵𝑨 𝑵𝑫 24. In a PN junction with no externally applied voltage, the drift and diffusion components of the holes and electrons currents Page 2 of 4  a. must sum to be zero b. must sum to be unity c. must sum to be 10 A d. must sum to be 10 mA 25. In semiconductor materials, the current that is caused by the difference in concentration is called a. diffusion current b. drift current c. both a and b d. none of the above 26. For a silicon crystal doped with boron. The acceptor concentration 𝑵𝑨 will be equal ……… if at T=300K, the electron concentration is 𝟏. 𝟓 × 𝟏𝟎𝟒 /𝒄𝒎𝟑 and intrinsic concentration 𝒏𝒊 = 𝟏. 𝟓 × 𝟏𝟎𝟏𝟎 /𝒄𝒎𝟑 a. 1.5 × 106 /𝑐𝑚3 b. 1.5 × 1026 /𝑐𝑚3 c. 1.5 × 1016 /𝑐𝑚3 d. 2.25 × 103 /𝑐𝑚3 27. For the following circuit, the silicon diode is ……… a. forward-biased b. reverse-biased c. equal zero d. a and b 28. For the circuit in the following figure, using constant drop voltage diode model, find the values of the voltage and current indicated (V, I) +2 𝑉 a. -2 V, 0.8 mA b. 0 V, 0.8 mA 5𝑘Ω c. 2 V, 0 mA d. -1.3 V, 0.66 mA −2 𝑉 29. For the circuit in the following figure, using ideal diode model, find the values of the voltage and current indicated (V,I) Page 3 of 4  a. 0 V, 2 mA b. 5 V, 2 mA c. 5 V, 0 A d. 0 V, 0 A 30. For the circuit in the following figure using ideal diode model, find the values of the voltage and current indicated (V, I) +𝟒 𝑽 a. -1 V, 0.5 mA 𝟖 𝒌𝛀 b. 0 V, 0.25 mA c. 0 V, 0.5 mA 𝑰 d. -1 V, 0 mA 𝟏𝟔 𝒌𝛀 −𝟒 𝑽 Best wishes Page 4 of 4