Elecs mod 3

• Field Effect Transistor


  unipolar device in which its action depends on

  one type of carrier.
• P Channel


  FET the carrier is a hole
• N Channel


  FET the carrier is an electron.
• FET


  three terminal device with source as a terminal where the carriers enters the bar.
• Drain


  the carriers leaves the bar
• GATE TERMINAL 


  controlling element
• Voltage Controlled Device


  The flow of carriers from source going to the drain

  is control by a voltage connected across the gate terminal that's why the FET is called
• Application of FET

  the FET can be used as a switch, an

  amplifier, multiplexer, an oscillator, a current limiter and a chopper.
• source, drain and gate.


  FET is made of three terminals
• source

  a terminal wherein the carriers enter the channel,
• Drain


  a terminal where the carriers leaves the channel
• Gate


  controls the flow of carrier from source to drain.
• two types of FET

  Junction Field

  Effect Transistor (JFET) and the Metal Oxide Semiconductor Field

  Effect Transistor (MOSFET) or

  an Insulated Gate

  Field Effect Transistor (IGFET).
• 2 types of JFET

  P CHANNEL, N CHANNEL
• N Channel JFET


  Schematic

  
• P Channel JFET


  SCHEMATIC

  
• source and the drain terminal, gate material


  For JFET N Channel the construction is it connects the _ _ and the P Channel represents _
• Reverse Bias 


  JFET: To put it in operation a forward bias should be connected to source and the drain is
• Source ; Drain


  For N channel JFET a negative terminal of battery is connected to the n channel ____ and

  the positive terminal is connected to the ____ material.
• negative supply voltage ; positive drain terminal.


  In N channel JFET This ____ of the source terminal will repel electrons away from the source material and it will be attracted by the
• Saturation 


  JFET: As voltage is increase therefore the flow of carrier from source to drain

  will also increase up to a certain level that it will reach what we called
• Drain-Source saturation current


  JFET: when voltage across the gate is zero.
• Pinch Off voltage (VP)


  The drain-source voltage when no increase in current anymore

  is called
• The reverse voltage applied across the gate will decrease the flow of current from source to drain due to depletion region occurs between gate - source and gate - drain material.
• JFET: Take note that this depletion region is voided with carrier.
• JFET: As We increase voltage across the gate, the drain current also decreases which is lowered than the Drain saturation Current (IDss).
• The MOSFET construction is that a material

  called substrate of P Type or N type is use.
• in the MOSFET gate terminal is insulated from the channel by a silicon dioxide SiO2 acting as an insulator.
• silicon dioxide insulator is a metal. That's why the

  FET is called Metal Oxide FET, its composition of metal and silicon

  dioxide.
• MOSFET are classified into two by its constructions. One is called Depletion MOSFET or DMOS and the other one is called Enhancement MOSFET or EMOS.
• There are other types of

  MOSFET we have VMOSFET (Vertical MOSFET),UMOSFET U-shaped MOSFET, and

  LDMOSFET (Laterally Diffused MOSFET),
• MOSFETs are use in digital circuits,

  switching circuits, amplifiers and for high power transistor applications.
• In order to operate a Depletion MOSFET, the source terminal should be

  forward bias and the drain is reverse bias, while the gate terminal can be

  supplied by a positive and negative battery as compare to JFET only a single

  supply and reverse bias was applied.
• The current flowing from source to drain

  can be increase or decrease depending upon the bias connected to the gate of

  DMOSFET.
• N Channel of DEPLETION MOSFET


  Schematic

  
• P Channel of Depletion MOSFET


  Schematic

  
• If the voltage across the gate is change to positive the current flowing from source to drain will increase more than the Drain Saturation Current (IDss)
• If the voltage across the source-gate is increase up to a level of pinch off voltage the current will reach the saturation point. As we increase the positive voltage of the gate therefore current ID also increase.
• This device DMOS can be operated with positive and

  negative voltage across the gate which controls the flow of current.
• Drain Current ID is solve using Schockleys formula.