This document describes semiconductors and diodes. It defines semiconductors as materials that conduct electricity better than insulators but not as well as conductors. N-type and P-type semiconductors are described based on adding impurities that add free electrons or holes. A diode consists of a P-N junction where current can only flow in one direction. Diodes can be used as rectifiers to convert alternating current to direct current in either half-wave or full-wave configurations. A capacitor can be used to smooth the rectified output voltage and current.

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

3. SEMICONDUCTOR
S ARE….
MATERIALS WHICH CAN
CONDUCT ELECTRICITY BETTER THAN
INSULATOR,
BUT NOT AS WELL AS CONDUCTORS.

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
Intrinsic Extrinsic
Pure materials Pure materials
+
Impurity element
•Increase conductivity
Pentavalent atoms Trivalent atoms

6. THE DOPING OF
SEMICONDUCTOR
S
THE PROCESS OF ADDING OF A CERTAIN AMOUNT OF
SPECIFIC IMPURITIES ATOMS IN THE PURE
SEMICONDUCTOR.
INCREASE ELECTRIC CONDUCTIVITY.

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".

9. Semiconductor diode

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
+ -

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
- +

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. .

14. HALF-WAVE RECTIFIER
• 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
• 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.

17. CAPACITOR SMOOTHING
ACTS AS A CURRENT REGULATOR
OR SMOOTHER

18. To CRO
To CRO
Without capacitor Graph without capacitor
With capacitor - Smoothing process

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

20. COMPONENTS OF
COMPUTERS

21. THE END