CECS311_Midterm_Sample (1)

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California State University, Long Beach *

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311

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Electrical Engineering

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Jan 9, 2024

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pdf

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NAME: Gawdyyy69 STUDENT ID: Gawdyyy69 1. (2 pts) Reverse-breakdown voltage = maximum reverse bias a diode can withstand. FALSE, Max reverse Voltage = Max reverse bias a diode can withstand. 2. (2 pts) Avalanche current is the name given to the current that approaches infinite when a forward biased diode has no current limiting. TRUE 3. (2 pts) Silicon diodes are preferred for small signals. TRUE 4. (2 pts) A Half-Wave Rectifier uses 2 diodes. FALSE, Half-wave rectifier → 1 diode Full-wave rectifier → 2 , 4 diodes 5. (2 pts) The depletion region in a diode decreases when a diode is Forward Biased. TRUE 6. (2 pts) The typical V f of germanium is: 0.3 V to 0.4 V 7. (2 pts) if F ac = 2kHz, what is F ripple for a Half-Wave Rectifier? F ac = F ripple = 2kHz 8. (2 pts) if F ac = 1kHz, what is F ripple for a Full-Wave Rectifier F ripple = 2 x F ac (Given: F ac = 1 kHz) F ripple = 2 x 1 kHz = 2 kHz 9. (2 pts) To create a N-Type material, how many valence electrons should the dopant have? To create an N-Type material: ● Use a dopant with more valence electrons than the host semiconductor. ● Dopants from Group V of the periodic table, such as phosphorus (P) are commonly used. ● These dopants have five valence electrons allowing for the creation of an excess of electrons in the semiconductor.

10. (4pts) In the following circuit, calculate the value of R, given a desired Diode Current of I D1 = 8ma, I D2 = 8ma. V s = 22v, V fd1 = 1.2v, V fd2 = 2.4v R = 2.3k ohms 11. (6 pts) Solve the Following circuit: V1 = 20v, R1 = 10 Ω , R2 = 20 Ω , R3 = 10 Ω , R4 = 10 Ω , R5 = 10 Ω and R6 = 20 Ω In the circuit above find the current through and the voltage across each resistor. I R1 2 A V R1 20 V I R2 0.5 A V R2 10 V I R3 0.5 A V R3 5 V I R4 0.25 A V R4 2.5 V I R5 0.25 A V R5 2.5 V I R6 0.25 A V R6 5 V

12. (8 pts) Complete the schematic below to make a regulated power supply with Vout = 9v and ground clearly labeled. Use a Half-Wave rectifier and a fixed voltage regulator, label any part numbers that you use. Also specify an acceptable transformer ratio assuming a Vin of 100Vpk into the transformer and a max voltage into the regulator of 30v. Ignore a desired value for Vripple.

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13. (10pts) Fill in the table on the right for the circuit below. Neglect the boxes with X’s and the forward voltage V f of D 1 is 4V Rs R L Dz Vs V 16 V 4 V 4 V 20 Volts I 16 mA 4m 12 mA 16 mA Amps R 1k 1 k Ω X X Ω s P 0.256 W 0.016 W 0.048 W X Watts

14. (8 pts) Determine the Operating Mode of the following transistor circuit. You will need to find Ic and Vce. β (Beta) of Q1 = 50, VBB = 10v, VCC = 10v, Rb = 100k, Rc = 2k. Ans) Ib = 9.3 x 10^(-5) A Ic = 0.00465 A Vce = 0.7 V Operating Mode = Linear

15. Answer the following questions for the circuit below. Vac = 150 V RMS @ 80Hz, T 1 is a 9:1, D1 – D4 are 1N4001 rectifier diodes and R L = 100 Ω a) (2 pts) Assuming that C 1 is not present. What is V pk across R L ? b) (2 pts) Calculate the value of C 1 in order to give us a Vripple of 800mv. c) (2 pts) What is the Average DC voltage across R L given the previously calculated smoothing capacitor? d) (4 pts) Assuming that in place of R L we connected an LM317, What is the largest regulated voltage we could generate without dropping out of regulation? e) (4 pts) Draw the LM317 circuit and calculate the values of R1 and R2 for an 8v regulator. R1 = R2 =

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16. (5pts) Assume D 1 is a 1n4001 and Vs is 10V pk . Draw one cycle of the waveform for Vs and Vout on the graph below. What is Vout in peak-peak voltage? -9.3 V 17. (5pts) Assume D 1 is a is a 1n4001 and Vs is 8V Pk, Draw one cycle of the waveform for Vs and Vout on the graph below. What is Vout in peak-peak voltage? 8.7 V 18. (5pts) Assume D 1 is a 1n4001 and Vs is 8V RMS . Draw the waveform of Vs and Vout on the graph below. What is the peak-peak voltage of Vout? 12.014 V