MODULE 4.1Semiconductors - Diode
Syllabus for Diode Diode symbols Diode characteristics and properties Diodes in series and parallel Main characteristi...
Diode and One Way Valve Diodes are similar to check valves. They allow fluid to flow in one direction  but not the rever...
How Diode Works The PN junction consists of P and N  material joint together. The area where P material meets the N  mat...
Current in N-Type Material          The flow is made up of           electron, similar to the           current in copper...
Current Flow in P-TypeMaterial             Holes flow within the              semiconductor from              +ve termina...
Junction Barrier                                              Both N and P types                                         ...
Barrier Junction   Video
Forward Biased PN Junction
Reverse Biased PN junction                Reverse biased                 ◦ No current due to                   majority c...
PN Junction Characteristic              The resistance is               given by ohm’s               law.              E...
Diode Identification… As there are many types of diode, a system is  required to identify it. The semi conductor identif...
…Diode Identification                     As there are many types of                      diode, a system is required to ...
Diode Markings                  There is the needs                   to identify                   anode/cathode         ...
Diodes Color Code                 Example                  ◦ Brown, orange and                    white bands            ...
Diode Maintenance
Diode Maintenance… Diodes are rugged and design to last  a long time. Damages can be due to:    ◦ Current overloads can ...
… diode maintenance   The followings are the precautions    when working with diodes:    ◦ Power off when installing and ...
Checking Diodes - analogue            Checking Diode –             Positive lead is black+   –       Why?+ –
Checking Diodes digital   Fwd bias – about 1      Reverse bias – open    K                        circuit.
Different Types of Diodes
… Different Types of Diodes ◦   Point Contact Diode ◦   PN Junction ◦   Schottky diodes ◦   Schottky Barrier Diode ◦   Var...
Different Types of Diodes …   Different types of    diodes are    manufactured for    different purposes:    ◦ Laser diod...
LED – Light Emitting Diode
Photodiode    When light strikes, it produces     electrons or holes causing current     flow.    Used to detect light. ...
Diode – PINDiode   The pin diode acts as an ordinary diode at    frequencies up to about 100 megahertz,    but above this...
Point Contact Diode     A point-contact diode works the same as      the junction diodes, but their construction is      ...
Schottky Diodes  Lower forward voltage drop about 0.15   – 0.4 v  Different Construction – metal to   semiconductor cont...
Schottky BarrierDiodes    Use for rectification     Shorter reverse time thus suited for     high frequency switching.
Diode SwitchingCharacteristics When diode is switched from forward biased  to reverse biased state or vice versa, it take...
Zener Diode
RESOURCES                    CAA UK Recommended BooksMy Blog            Title                      Author     ISBN        ...
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EASA Part 66 Module 4 diode

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This slide is designed as a teaching aid for students pursuing Module 4 in EASA B1 examination. There are a few topics not covered in this slide

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EASA Part 66 Module 4 diode

  1. 1. MODULE 4.1Semiconductors - Diode
  2. 2. Syllabus for Diode Diode symbols Diode characteristics and properties Diodes in series and parallel Main characteristics and use of silicon controlled rectifiers (thyristors), light emitting diode, photo conductive diode, varistor, rectifier diodes; Functional testing of diodes
  3. 3. Diode and One Way Valve Diodes are similar to check valves. They allow fluid to flow in one direction but not the reversed.
  4. 4. How Diode Works The PN junction consists of P and N material joint together. The area where P material meets the N material is called the junction.
  5. 5. Current in N-Type Material  The flow is made up of electron, similar to the current in copper.  The electrons leave the crystal and flow towards the positive terminals of the battery.
  6. 6. Current Flow in P-TypeMaterial  Holes flow within the semiconductor from +ve terminal to -ve.  The flow external to the semiconductor is always electron.
  7. 7. Junction Barrier  Both N and P types of semiconductors are electrically neutral.  The number of electrons andWhat happen, the electrons from Nmaterial move to P material, thus creating protons is balanced.++ ions on N material.  We expected theThe hole transferred to N material.This create a field barriers, ++ at N electrons willmaterial and -- at P material. neutralize and balance the holes, but that do not
  8. 8. Barrier Junction Video
  9. 9. Forward Biased PN Junction
  10. 10. Reverse Biased PN junction  Reverse biased ◦ No current due to majority carrier. ◦ small current due to minority carrier.  Resistance characteristic. ◦ Small resistance in forward bias ◦ High resistance in in reversed bias. Refer to the graph.
  11. 11. PN Junction Characteristic  The resistance is given by ohm’s law.  Example, forward bias, at 1 v point, R=250 ohms. In reverse bias – R= 800k.
  12. 12. Diode Identification… As there are many types of diode, a system is required to identify it. The semi conductor identification is used to distinguish one from the other.
  13. 13. …Diode Identification  As there are many types of diode, a system is required to identify it.  The semi conductor identification is used to distinguish one from the other.• The first digit XN – X =is the number of junction. N = a semiconductor.• YYY – Identification Number.
  14. 14. Diode Markings  There is the needs to identify anode/cathode  The cathode is marked as “k”, “+” or color code or band. 
  15. 15. Diodes Color Code  Example ◦ Brown, orange and white bands  Brown = 1  Orange = 3  White 9 ◦ So the diode is 1N139
  16. 16. Diode Maintenance
  17. 17. Diode Maintenance… Diodes are rugged and design to last a long time. Damages can be due to: ◦ Current overloads can damage the junction ◦ Excess voltage ◦ High temperature. Heat increases the current flow which in turn produce more heat which will cause higher current.
  18. 18. … diode maintenance The followings are the precautions when working with diodes: ◦ Power off when installing and removing diodes ◦ Do not use force to pull the diode from the PCB. ◦ Soldering diode need care to avoid excessive heat. ◦ Replace of diode – must be direct replacement, right direction. ◦ Avoid touching the exposed wires to avoid static electricity.
  19. 19. Checking Diodes - analogue  Checking Diode – Positive lead is black+ –  Why?+ –
  20. 20. Checking Diodes digital Fwd bias – about 1  Reverse bias – open K circuit.
  21. 21. Different Types of Diodes
  22. 22. … Different Types of Diodes ◦ Point Contact Diode ◦ PN Junction ◦ Schottky diodes ◦ Schottky Barrier Diode ◦ Varicap or varactor diode ◦ Zener diode
  23. 23. Different Types of Diodes … Different types of diodes are manufactured for different purposes: ◦ Laser diode – the diode produces laser light. The laser generation function is cheaper than the alternative, however the diode is more expensive than other types of diodes.
  24. 24. LED – Light Emitting Diode
  25. 25. Photodiode  When light strikes, it produces electrons or holes causing current flow.  Used to detect light.  Typically photo-diodes are operated under reverse bias conditions where even small amounts of current flow resulting from the light can be easily detected.
  26. 26. Diode – PINDiode  The pin diode acts as an ordinary diode at frequencies up to about 100 megahertz, but above this frequency the operational characteristics change.  The large intrinsic region increases the transit time of electrons crossing the region. Above 100 megahertz, electrons begin to accumulate in the intrinsic region. The carrier storage in the intrinsic region causes the diode to stop acting as a rectifier and begin acting as a variable resistance.
  27. 27. Point Contact Diode  A point-contact diode works the same as the junction diodes, but their construction is simpler.  A block of n-type semiconductor is built, and a conducting sharp-point contact made with some group-3 metal is placed in contact with the semiconductor.  Some metal migrates into the semiconductor to make a small region of p-type semiconductor near the contact.  The long-popular 1N34 germanium version is still used in radio receivers as a detector and occasionally in specialized analog electronics.
  28. 28. Schottky Diodes  Lower forward voltage drop about 0.15 – 0.4 v  Different Construction – metal to semiconductor contact  Mainly used for clamping circuit
  29. 29. Schottky BarrierDiodes Use for rectification  Shorter reverse time thus suited for high frequency switching.
  30. 30. Diode SwitchingCharacteristics When diode is switched from forward biased to reverse biased state or vice versa, it takes finite time to attain a steady state. This time consists of a transient and an inter val of time before the diode attain the steady state is attained. The behavior of the diode during this time is called switching characteristics of the diode. In the forward-bias state, there are a large number of electrons from the n side diffusing to the p side. This diffusion process establishes a large nu mber of minority carriers in each material
  31. 31. Zener Diode
  32. 32. RESOURCES CAA UK Recommended BooksMy Blog Title Author ISBN Aircraft Electricity and Eisman 0-02-801859-1 Electronics Art of Electronics Horowitz 0-521-37095-7 Horowitz /Hill /Hill Elements of Hickey/ 0070286957 Electronics Villines Modern Aviation Helfrich 0-13-118803-8 Electronics Micro Electronics in E Pallet 0-273-08612-X Aircraft systems
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