150 LECTURE on all kinds of diodes 15 DIODES.ppt

diodes

1. SEMICONDUCTORS
LECTURE 15 DIODES

2. YOU TUBE :Description of the Silicon Atomhttp://www.youtube.com/watch?v=Wvd3hj93Iog
LECTURE#15
SEMICONDUCTORS ARE CRYSTALS THATHAVE THE PROPERTIES OF BOTH A CONDUCTOR
AND A INSULATOR. SILICON (MOSTLY SAND, 27.75 OF EARTH’S CRUST) IS THE MOST COMMON.
SILICON HAS 4 ELECTRONS IN ITS OUTER SHELL (VALENCE). IT WOULD LIKE AN ADDITONAL 4
FOR A OVERALL NEUTRAL CHARGE. IT DOES THIS BY SHARING ELECTRONS WITH OTHER
SILICON ATOMS.
VALENCE ELECTRONS
THIS STRUCTURE IS NOW A CRYSTAL

3. PURIFIED SILICON

4. N TYPE ATOM
P TYPE ATOM
PURE SILICON MUST HAVE TRACT AMOUNTS OF OTHER ELEMENTS ADDED TO IT
TO MAKE IT A SEMICONDUCTOR. BORON AND PHOSPHORUS ARE THE MOST COMMON
USED, THIS PROCESS IS CALLED DOPING.
BORON HAS 3 ELECTRONS IN ITS OUTER SHELL WHEN ADDED TO SILICON THIS LEADS TO A
DEFICIENCY OF 1 VALENCE ELECTRON (CALLED A HOLE) THIS GIVES THE SILICON A OVERALL
POSITIVE CHARGE. THIS IS CALLED P TYPE SILICON. THESE HOLES CAN MOVE THRU THE CRYSTAL
AND CARRY CURRENT.
PHOSPHORUS HAS 5 ELECTRONS IN ITS OUTER SHELL WHEN ADDED TO SILICON THIS LEADS TO A
EXCESS OF 1 VALENCE ELECTRON THIS GIVES THE SILICON A OVERALL NEGATIVE CHARGE. THIS IS
CALLED N TYPE SILICON. THESE ELCTRONS CAN MOVE THRU THE CRYSTAL AND CARRY CURRENT.

5. YOU TUBE : Semiconductors Theory 1 Segment 2A - Doped Silicon Crystal http://www.youtube.com/watch?v=cRvJouvITug

6. http://www.youtube.com/watch?feature=endscreen&v=LWfCqpJzJYM&NR=1Silicon Wafer Processing Animation

7. MAKE presents: The Diode
http://www.youtube.com/watch?v=AqzYsuTRVRc
THE DIODE IS AN ELECTRONIC ONE WAY VALVE
BOTH P AND N TYPE SILICON CAN CONDUCT CURRENT.
BY BUTTING P AND N TYPE SILICON AGAINST EACH OTHER
CURRENT WILL FLOW IN ONE DIRCTION ONLY.THIS INTERFACE BEWTEEN
THE TWO IS CALLED A P-N JUNCTION
+ -
(ENCLOSED IN SMALL GLASS CYLINDER)
DIRECTION OF CURRENT FLOW

8. At the junction, free electrons from
the N-type material fill holes from the
P-type material. This creates an
insulating layer in the middle of the
diode called the depletion zone.
When the positive end of the circuit is hooked
up to the N-type layer and the negative end is
hooked up to the P-type layer, free electrons
collect on one end of the diode and holes
collect on the other. The depletion zone gets
bigger.
THIS DIODE IS REVERSE BIASED, NO CURRENT FLOWS

9. BY PLACING A POTENTIAL DIFFERENCE (VOLTAGE) ACROSS THE DIODE WITH THE
CORRECT POLARITY CURRENT WILL FLOW THRU THE DIODE. HOLES IN ONE
DIRECTION,ELECTRONS IN THE OTHER DIRECTION
When the negative end of the circuit is hooked up to
the N-type layer and the positive end is hooked up to
P-type layer, electrons and holes start moving and
the depletion zone disappears.
.Formation and Properties of Junction Diode - Physics .http://www.youtube.com/watch?v=4SlfaocMfdA
THIS DIODE IS FORWARD BIASED, CURRENT FLOWS

10. DIODE OPERATION
A DIODE WILL NOT CONDUCT UNTIL THE FOEWARD VOLYAGE REACHES
A CERTAIN LEVEL. FOR SICILON DIODES THIS IS ABOUT 0.6V.
IF THE FORWARD CURRENT BECOMES TOO GREAT THE DIODE MAY CRACK OR MELT. AT
THIS POINT THE DIODE MAY CONDUCT IN BOTH DIRECTIONS AND VAPORIZE THE CHIP.
TOO MUCH REVERSE VOLTAGE WILL CAUSE IT TO CONDUCT IN
THE WRONG DIRECTION WHICH WILL DESTROY THE CHIP.

12. TYPES OF DIODES
MANY TYPES EXIST
SMALL SIGNAL: CONVERT AC TO DC, DETECT RADIO SIGNALS, MULTIPLY VOLTAGE,
PERFORM LOGIC OPERATIONS.

13. POWER RECTIFIER
WORK AT MUCH HIGHER CURRENT LEVELS, CONSTRUCTED IN LARGE METAL PACKAGES
TO ABSORBE HEAT AND TRANSFER IT TO HEAT SINKS. USED MAINLY IN POWER SUPPILES

14. ZENER DIODES
WORK AT SPECIFIC BREAKDOWN VOLTAGE.
FUCTION AS A VOLTAGE SENSITIVE SWITCH.
THIS VOLTAGE (VZ) VARY FROM 2 TO 200 VOLTS

16. LIGHT EMITTING DIODE (LED)
ALL DIODES EMIT SOME EM RADIATION WHEN FORWARD
BIASED. DIODES MADE FROM CERTAIN SEMICODUCTORS EMIT
LOTS OF LIGHT. THESE ARE CALLED LEDS

17. YOU TUBE: MAKE presents: The LED
http://www.youtube.com/watch?v=P3PDLsJQcGI
LEDS CAN EMIT AND DETECT LIGHT

18. (PHOTODIODES)

19. http://www.youtube.com/watch?v=U6Wvmrc3akchow photodiode works
PHOTODIODES
ARE DESIGNED TO DETECT LIGHT. ( ALL PN JUNCTIONS ARE LIGHT SENSITIVE) THEY HAVE A
WINDOW WHERE LIGHT ENTERS TO A LARGE EXPOSED JUNCTION REGION. SOME COMMON
USES INCULDE CAMERAS, ALARMS, LIGHTWAVE DIODES (LASERS).
PHOTODIODE SYMBOL
PHOTODIODES CAN BE USED TO DETECT FAST
PULSES OF INFRARED LIGHT, USED IN LIGHTWAVE
COMMUNICATIONS

20. http://www.youtube.com/watch?v=U6Wvmrc3akcThe Photodiode
HOW PHOTODIODES WORK
A INCOMING PHOTON WILL CREATE A HOLE
ELECTRON PAIR AT THE PN JUNCTION. A CURRENT
WILL FLOW IF BOTH SIDES ARE CONNECTED.
INCOMING PHOTONS
-
+
HOLES
ELECTRONS

21. TYPES OF PHOTODIODES
SMALL AREA PHOTODIODES
THESE HAVE VERY FAST RESPONS TIMES
LARGE AREA PHOTODIODES
HAVE SLOWER RESPONSE TIMES THEN SMALL AREA PHOTODIODES
THESE LARGE SURFACE AREA GIVES HIGH SENSITIVITY.

22. WINDOW
METAL CAN
CHIP
LENS
ANODE
CATHODE
COMPOENTS OF A PHOTODIODE

23. DIFFERENT PACKAGE STYLES FOR PHOTODIODES

24. Any CCD
CHARGE COUPLED DEVICES (CCD)

25. anodecathode
symbol
cathode
anode
device
Silicon rectifier diode
_
+
0
+
_
0
+
_
Input voltage output voltage
circuit
Input and output of a simple rectifier circuit
Fig. 8-23 p.219 A single-phase half-wave rectifier circuit produces
one output pulse of dc for each cycle of ac input.
HOW DIODES ARE USED

26. Power Diode Rectifier
Half Wave Rectifier Circuit

27. Half-wave Rectifier with Smoothing Capacitor

  
                                                
 
                              

28. Full Wave Rectifier Circuit

  
                        
 
                        

29. The Diode Bridge Rectifier

  
                           
 
                                  
 
                                  
The Positive Half-cycle The Negative Half-cycle

30. Full-wave Rectifier with Smoothing Capacitor

  
                            
 
                                       
 
                                       
 
    
Full Wave Bridge Rectifierhttp://www.youtube.com/watch?v=aCfAdIRRw7M

32. VARIOUS TYPES OF POWER RECTIFIERS

33. Various printed circuit board mounted rectifiers and voltage regulators