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EELE 2321 – Electronics Spring, 2013 DIODES AND APPLICATIONS Eng. Wazen M. Shbair

EELE 2321 – Electronics Spring, 2013 DIODES AND APPLICATIONS Eng. Wazen M. Shbair. Content. Diode Operation Voltage-Current (V-I) Characteristics of a Diode Diode Models Half & Full -Wave Rectifiers Power Supply Filters and Regulators Diode Limiters and Clampers Voltage Multipliers.

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EELE 2321 – Electronics Spring, 2013 DIODES AND APPLICATIONS Eng. Wazen M. Shbair

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  1. EELE 2321 – Electronics Spring, 2013 DIODES AND APPLICATIONSEng. Wazen M. Shbair

  2. Content • Diode Operation • Voltage-Current (V-I) Characteristics of a Diode • Diode Models • Half & Full -Wave Rectifiers • Power Supply Filters and Regulators • Diode Limiters and Clampers • Voltage Multipliers

  3. Diode Operation • What is Diode? A diode is a semiconductor device with a single pn junction and metal connections to leads. It has the ability to pass current in only one direction.

  4. Typical diode packages Some common configurations are

  5. Forward bias • Forward bias Forward bias is the condition which allows current in the diode. The bias voltage must be greater than the barrier potential.

  6. Forward bias

  7. Reverse bias • Reverse biasReverse biasis the condition that essentially prevents current through the diode.

  8. Reverse bias

  9. Reverse bias • Reverse Current : The extremely small current that exists in reverse bias after the transition current dies out is caused by the minority carriers in the n and p regions that are produced by thermally generated electron-hole pairs

  10. V-I Characteristics of a Diode Forward bias Reverse bias

  11. V-I Characteristics of a Diode

  12. Diode Model- (Ideal model)

  13. Diode Model- (Practical model)

  14. Diode Model- (Complete model)

  15. Summary Example 2-1 Page 43

  16. HALF-WAV ERECTIFIERS • Electronic devices require a source of constant dc (battery , dc power supply) • The dc power supply converts the standard 120 V/220V, 60 Hz ac voltage into a constant dc voltage.

  17. Half-Wave Rectifier Operation • The diode conducts during the positive half cycle, It does not conduct during the negative half cycle.

  18. Half-Wave Rectifier Operation Question ? What is the output if the diode is reversed?

  19. Half-Wave Rectifier Operation • Average Value of the Half-Wave Output Voltage • The average value of the half-wave rectified output voltage is the value you would measure on a dc voltmeter

  20. Half-Wave Rectifier Operation • Effect of the Barrier Potential on the Half-Wave Rectifier Output • When the practical diode model • is used with the barrier potential of 0.7 V taken into account.

  21. -Vp(in) • Peak Inverse Voltage (PIV) • It is equal to the peak input voltage and is the maximum voltage across the diode when it is not conducting. PIV at tp

  22. Half-Wave Rectifier Operation • Transformer Coupling • a transformer is often used to couple the ac input voltage from the source to the rectifier. • It provides two advantages. First, it allows the source voltage to be stepped down. Second, the ac source is electrically isolated from the rectifier

  23. The amount that the voltage is stepped down is determined by the turns ratio of the transformer. • turns ratio = The number of turns in the secondary (Nsec) divided by the number of turns in the primary (Npri)

  24. Full-wave Rectifier • Half-wave rectifiers have some applications, the full-wave rectifier is the most commonly used type in dc power supplies. • You will learn about two types of full-wave rectifiers: • Center-tapped • Bridge.

  25. Full-wave Rectifier • The number of positive alternations that make up the full-wave rectified voltage is twice that of the half-wave voltage for the same time interval

  26. Center-Tapped Full-Wave Rectifier • A center-tapped rectifier is a type of full-wave rectifier that uses two diodes connected to the secondary of a center-tapped transformer

  27. Center-Tapped Full-Wave Rectifier

  28. Center-Tapped Full-Wave Rectifier

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