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.

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

9. MRSMKL 9
Semiconductor diode

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

20. The End
MRSMKL 20