E-Devices T1-S1 - Answers PDF

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MANDALAY TECHNOLOGICAL UNIVERSITY DEPARTMENT OF MECHATRONIC ENGINEERING McE -31026 Electronics Devices I Tutorial- I 13.2.2019(Wed) Sr.No. Questions Mark Write down the following statements.(TRUE or FALSE) 12 1. The two regions of a diode are the anode and the collector. (True/False) F 2. A basic half-wave rectifier consists of one diode. (True/False) T F 3. The purpose of the capacitor filter in a rectifier is to convert ac to dc. (True/False) T 4. The zener diode normally operates in reverse breakdown. (True/False) F 5. The varactor diode normally operates in forward bias. (True/False) T 6. The reverse current of a photodiode increases as the incident light increases. (True/False) (d) 7. The peak value of the input to a half-wave rectifier is 10 V. The approximate peak value of the output is (a) 10 V (b) 3.18 V (c) 10.7 V (d) 9.3 V (a) 8. When a 60 Hz sinusoidal voltage is applied to the input of a full-wave rectifier, the output frequency is (a) 120 Hz (b) 60 Hz (c) 240 Hz (d) 0 Hz (b) 9. Load regulation is determined by (a) changes in load current and input voltage (b) changes in load current and output voltage (c) changes in load resistance and input voltage (d) changes in zener current and load current (a) 10. The cathode of a zener diode in a voltage regulator is normally (a) more positive than the anode (b) more negative than the anode (c) at +0.7 V (d) grounded 11. An LED (c) (a) emits light when reverse-biased (b) senses light when reverse-biased (c) emits light when forward-biased (d) acts as a variable resistance 12. The internal resistance of a photodiode (b) (a) increases with light intensity when reverse-biased (b) decreases with light intensity when reverse-biased (c) increases with light intensity when forward-biased (d) decreases with light intensity when forward-biased 13. Consider the circuit in Figure (1).

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Figure (1) (a) What type of circuit is this? (b) What is the total peak secondary voltage? (c) Find the peak voltage across each half of the secondary. (d) Sketch the voltage waveform across RL. (e) What is the peak current through each diode? (f) What is the PIV for each diode? Solution (a) Center-tapped full-wave rectifier Page 1 of 3

(b) V psec  0.25 1.414 120V  42.42V (c)

Vp  sec 



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(d) V RL 

42.42  21.21V 2

V p sec 2

 0.7V  20.51V V p  sec 

(e) I F 

 0.7V 2  20.51mA 1.0k 

V RL  RL

(f) PIV 

Vp  sec  2

 V RL  41.72V

20.51V

14. To what value must R be adjusted in Figure (2) to make IZ = 40 mA? Assume VZ = 12 V at 30 mA and ZZ = 30 Ω.

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Figure (2) Solution

2 15. Determine how to connect the seven-segment display in Figure(3) to display “5.” The maximum continuous forward current for each LED is 30 mA and a +5 V dc source is to be used.

Figure(3) Solution Page 2 of 3

*************** End Of Questions ***************

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