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3. 3/2/2016 Page 3Numeral Systems What is a Diode ? An electronic component that allows the current flow in one direction only. It has with two electrodes called the anode and the cathode. Most diodes are made with semiconductor materials such as silicon, germanium.semiconductor Application of diode Rectification :- A rectifier changes AC (Alternating Current) to DC (Direct Current ) This is the most important application of diodes. 17/11/2014 page 3

4. Types of Diodes Normal Diodes Light-Emitting Diodes (LEDs) Schottky Diodes Zener Diodes 4 17/11/2014 page 4

5. 3/2/2016 Page 5Numeral Systems How a diode works 17/11/2014 page 5

6. 3/2/2016 Page 6Numeral Systems Forward Operation 17/11/2014 page 6 In forward operation the anode connected to the positive electrode of the source and the cathode connected to the negative electrode of the source. In this situation the current flows in the circuit. The current flows in the Circuit.

7. 3/2/2016 Page 7Numeral Systems Reverse Operation In reverse operation the anode connected to the negative electrode of the source and the cathode connected to the positive electrode of the source. No current ( very small ) flows in in the circuit. 17/11/2014 page 7

8. 3/2/2016 Page 8Numeral Systems 17/11/2014 page 8 curve for a real diode.

9. 17/11/2014 page 9 Forward and Reverse Operation Practical Exercise :-

10. 3/2/2016 Page 10Numeral Systems 17/11/2014 page 10 Partner Work

11. 3/2/2016 Page 11Numeral Systems Partner Work 17/11/2014 page 11 In short sentence:- Q1 :- Define a diode ?  A diode is a electronic component that allows the current flow in one direction only. Q2 :- Draw a symbol of diode ? Q3 :- what is the difference between forward biased and reverse biased ?  In forward biased the current flows in the circuit.  In reverse biased no current flows in the circuit.

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13. 3/2/2016 Page 13Numeral Systems 17/11/2014 page 13 Example ( 1 ) :- Example ( 1 ) :- Assume the diode in the circuit below is ideal. Determine the value of I D if : a) V A = 5 volts (Forward Bias) b) V A = -5 volts (Reverse Bias)

14. 3/2/2016 Page 14Numeral Systems 17/11/2014 page 14 Solution :- a) With VA > 0 the diode is in forward bias and is acting like a perfect conductor so:  ID = VA / RS = 5 V / 50  = 0.1 A b) With VA < 0 the diode is in reverse bias and is acting like a perfect insulator, therefore no current can flow and ID = 0.

15. Group Work 17/11/2014 page 15

16. 3/2/2016 Page 16Numeral Systems Group Work 17/11/2014 page 16 Assume the diode in the circuit below is ideal. Determine the value of I D if : a) V A = 10 v (Forward Bias) b) V A = -10 v (Reverse Bias)

17. 3/2/2016 Page 17Numeral Systems Group Work 17/11/2014 page 17 Solution :- a) With VA > 0 the diode is in forward bias and is acting like a perfect conductor so: ID = VA / RS = 10 V / 80 = 0.125 A b) With VA < 0 the diode is in reverse bias and is acting like a perfect insulator, therefore no current can flow and ID = 0.

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