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    Power Electronic

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    kalyan mondal
    The document discusses the working principle of a power transistor. It explains that a transistor is a three-terminal semiconductor device that can be used as an amplifier or switch. The document then describes the different terminals, currents, and voltages in a transistor. It explains the cutoff, saturation, and active regions of operation and the biasing conditions needed for each region.

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    Download as PPTX, PDF, TXT or read online from Scribd

    Power Electronic

    Uploaded by

    kalyan mondal
    14 views10 pages
    The document discusses the working principle of a power transistor. It explains that a transistor is a three-terminal semiconductor device that can be used as an amplifier or switch. The document then describes the different terminals, currents, and voltages in a transistor. It explains the cutoff, saturation, and active regions of operation and the biasing conditions needed for each region.

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    The document discusses the working principle of a power transistor. It explains that a transistor is a three-terminal semiconductor device that can be used as an amplifier or switch. The document then describes the different terminals, currents, and voltages in a transistor. It explains the cutoff, saturation, and active regions of operation and the biasing conditions needed for each region.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    14 views10 pages

    Power Electronic

    Uploaded by

    kalyan mondal
    The document discusses the working principle of a power transistor. It explains that a transistor is a three-terminal semiconductor device that can be used as an amplifier or switch. The document then describes the different terminals, currents, and voltages in a transistor. It explains the cutoff, saturation, and active regions of operation and the biasing conditions needed for each region.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 10

    IDEAL INSTITUTE OF ENGINEERING

    NAME - KALYAN MONDAL


    ROLL - 27901621046
    DEPARMENT - ELECTRICAL
    YEAR- - 3RD YEAR(5TH SEM)
    SUBJECT - POWER ELECTRONIC
    TOPIC - WORKING PRINCIPAL OF
    POWER TRANSISTOR
    INTRODUCTION
    What is transistor?
    A three-terminal device whose output current, voltage
    and/or power are controlled by its input.

    Commonly used in audio application as an amplifier, in


    switching application as a switch and in power supply
    voltage and current regulator circuit.

    2 basic transistor types: BJT and FET


    These two transistor differ in their operating
    characteristic and their internal construction.
    Transistor Currents
     The directions of the currents in npn transistor and
    pnp transistor are shown in the figure.
     The emitter current (IE) is the sum of the collector
    current (IC) and the base current (IB)
     IB << IE or IC
     The capital letter – dc value
     Transistor is a current-controlled device - the value of
    collector and emitter currents are determined by the
    value of base current.
     An increase or decrease in value of IB causes similar
    change in values of IC and IE.
    Transistor Voltages
     VCC – collector supply voltage. This is a power supply
    voltage applied directly to collector of transistor.
     VBB – base supply voltage. this is dc voltage used to bias
    base of transistor.
     VEE – emitter supply voltage. dc biasing voltage and in
    many cases, VEE is simply a ground connection.
    BJT OPERATION
    To operate the transistor properly, the two pn
    junction must be correctly biased with external dc
    voltages.
    The figure shown the proper bias arrangement for
    both npn and pnp transistor for active operation as
    an amplifier.
    Transistor is made of 3 separate semiconductor
    materials that joined together to form two pn
    junction.
    Point at which emitter and base are joined forms a
    single pn junction  base-emitter junction
    Collector-base junction  point where base and
    collector meet.
    Cutoff region
    Both transistor
    junctions are reverse
    biased.
    With large depletion
    region between C-B and
    E-B, very small amount
    of reverse current, ICEO
    passes from emitter to
    collector and can be
    neglected.
    So, VCE = VCC
    Saturation region

     Both transistor junctions are


    forward-biased.
     IC reaches its maximum
    value as determined by VCC
    and total resistance in C-E
    circuit.
     IC is independently from
    relationship of β and IB.
     VBE is approximately 0.7V
    and VCE < VBE. VCC
    IC 
    RC  RE
    Active region
    BE junction is forward
    biased and the BC
    junction is reverse biased.
    All terminal currents have
    some measurable value.
    The magnitude of IC
    depends on the values of
    β and IB.
    VCE is approximately near
    to 0.7V and VCE falls in
    ranges VBE<VCE<VCC.
    Summary
    A transistor can be operated as an electronics
    switch.
    When the transistor is off it is in cutoff condition
    (no current).
     When the transistor is on, it is in saturation
    condition (maximum current).
     Beta can vary with temperature and also varies
    from transistor to transistor.

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