4.2 semiconductor diode (1)
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This document discusses semiconductors and semiconductor diodes. It describes how semiconductors have conductivity between insulators and conductors, and how their conductivity can be increased through doping with impurities. It defines intrinsic and extrinsic semiconductors, and n-type and p-type semiconductors which are created through doping with pentavalent or trivalent impurities. The document goes on to describe semiconductor diodes, how they function as rectifiers in both half-wave and full-wave configurations, and how a capacitor can be used to smooth the output voltage of a rectifier circuit.
4.2 semiconductor diode (1)
- 1. MRSMKL 1
- 2. Learning outcomes… • Describe semiconductors in terms of resistance and free electrons. • Describe n-type and p-type semiconductors. • Describe semiconductor diodes. • Describe the function of diodes • Describe the use of diodes as rectifiers • Describe the use of capacitor to smooth output current and output voltage in a rectifier circuit MRSMKL 2
- 3. Semiconductor are…. • materials which can conduct electricity better than insulator, but not as well as conductors. MRSMKL 3
- 4. MRSMKL 4 •4 electrons in outermost orbit. •in covalent bonding. •atoms vibrate causes electron to break free from the bonds. •Electron free leaves hole. •Semiconductor has 2 types of charge carriers. Properties of semiconductor
- 5. Type of semiconductors MRSMKL 5 Intrinsic Extrinsic Pure materials Pure materials + Impurity element •Increase conductivity Pentavalent atoms Trivalent atoms
- 6. The Doping of Semiconductors • The process of adding of a certain amount of specific impurities atoms in the pure semiconductor. • Increase electric conductivity. MRSMKL 6
- 7. • Pentavalent impurities. • 5 valence electron. • contributing extra free electrons. • produce n-type semiconductors. • Trivalent impurities • 3 valence electrons • produce p-type semiconductors • producing a "hole". MRSMKL 7
- 8. MRSMKL 8
- 10. MRSMKL 10 p-type n-type Positive hole Negative electron Symbol p-n junction p-n junction (Semiconductor diode)
- 11. Diode in Forward-biased • p-type of the diode is connected to …………………. • n-type is connected to the …………………… of the battery. • Electron moves across the p-n junction • Current flow through the circuit • Diode is forward biased MRSMKL 11 + -
- 12. Diode in Reverse-biased • p-type of the diode is connected to …………………. • n-type is connected to the …………………… of the battery. • Electrons and holes pulled away from the p-n junction • No Current flow through the circuit • Diode is reverse biased MRSMKL 12 - +
- 13. Diode as rectifier • A.C to D.C. • Rectification is a process to convert an alternating current into a direct current by using a diode. . MRSMKL 13
- 14. Half-wave rectifier MRSMKL 14 • First half –cycle, diode is forward biased •Current flow through the circuit •Second half-cycle, diode is reversed biased •No current flow •Diode as half-wave rectifier
- 15. Full -wave rectifier MRSMKL 15 • First half –cycle, diode ____________are forward biased •Current flow through the circuit •Second half-cycle, diode ___________are forward biased • Current flow through the circuit •Diode as full -wave rectifier To CRO a .
- 16. MRSMKL 16
- 17. Capacitor smoothing Acts as a current regulator or smoother MRSMKL 17
- 18. MRSMKL 18 To CRO a To CRO a.
- 19. • As the output voltage increases, the capacitor is charged, • When the output voltage falls back to zero, the capacitor releases its charge (discharge current) • Steady output voltage is maintain across a resistor MRSMKL 19