Your SlideShare is downloading. ×
0
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Bipolar Transistor Operation
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Bipolar Transistor Operation

6,504

Published on

Theory of operation of a bipolar transistor including a practical application.

Theory of operation of a bipolar transistor including a practical application.

0 Comments
3 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
6,504
On Slideshare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
171
Comments
0
Likes
3
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Sean Degnan
    Bipolar Transistor Operation
  • 2. Bipolar Transistor Function & Construction
    A bipolar transistor is a semi-conductor device that acts as a variable resistor
    Applications
    Amplifiers
    Voltage and Current Regulators
    Electronic Switches
    • Made up of three alternating layers, which form two P-N junctions.
    • 3. Emitter: heavily doped region that supplies majority current carriers.
    • 4. Base: Thin and lightly doped region that controls current flow through the transistor.
    • 5. Collector: Large, lightly doped region used to collect current carriers from emitter.
  • Simplified Drawing & Schematic Symbol
    Construction drawing can be simplified as a “sandwich” of semiconductor materials.
    Can be either NPN or PNP transistor
    Schematic Symbol: Arrow always points between base and emitter
    Direction designates type
    NPN = Not Pointing iN
    PNP = Pointing iNProperly
    Also points in direction of conventional current flow
    Collector
    Base
    Emitter
    Collector
    Base
    Emitter
  • 6. Biasing Requirements
    Base to Emitter Junction (VBE)
    Forward biased for majority current carriers to flow from emitter to base, where they become minority carriers
    Base to Collector Junction (VBC)
    Reverse biased to allow minority current carriers from the emitter flow from base to collector
    Collector
    VBC
    Q1
    Base
    VBE
    Emitter
  • 7. Steady-State Operation
    P
    N
    N
    With the Base to Emitter Junction forward biased, majority current carriers flow from emitter to base, where they become minority carriers
    This is emitter current (IE)
    Since the base is thin and lightly doped, very few current carriers recombine in the base
    This is base current (IB)
    The rest of the current carriers are swept across the base to collector junction
    This is collector current (IC)
    E
    C
    B
    IE
    IC
    IB
    Electron
    Current Flow
    Conventional
    Current Flow
  • 8. Transient Operation (VBE)
    P
    N
    N
    Base to emitter junction is forward biased
    Low resistance, so small  in VBE causes a large  in IE
    The base is thin and lightly doped
    Few current carriers recombine to form more base current
    IB  only slightly
    The rest of the current carriers are swept across the base to collector junction
    IC  greatly
    E
    C
    B
  • 9. Bipolar Transistor Characteristics
    Current Relationships
    Emitter current equals base current plus collector current
    Alpha (α): Ratio of Collector Current to Emitter Current
    Typically 0.95 – 0.98
    Beta (β): Ratio of Collector Current to Base Current
    Ranges from 40 to >100 depending on application
    Gamma (γ): Ratio of Emitter Current to Base Current
    Slightly greater than β
  • 10. Bipolar Transistor Characteristics
    Typical Characteristic Curve
    Shows relationship between IB, IC and VCE
    IC relatively constant for a given VCE
    IC dependant on IB
    Saturation
    IC no longer increases for an increase in IB
    IC is maximum
    VCE is minimum (VCE ≈ 0.2VDC)
    “ON” state when used as a switch
    Cutoff
    Transistor not biased to conduct
    IB, IC, IE = 0A
    VCE is maximum for circuit
    “OFF” state when used as a switch
    Saturation
    Cutoff
  • 11. Bipolar Transistor Characteristics
    Load Line
    Straight line drawn between saturation and cutoff, representing range of operating points
    Quiescent Point (Q-Point)
    The steady-state values of IB, IC, and VCE with no AC input applied
    Determined by circuit design
    Saturation
    Q-Point
    Cutoff
    Load Line
  • 12. Common Emitter Configuration
    +VCC
    Emitter is “common” to both input and output
    Input applied to base to change VBE
    Output taken from collector
    Gain
    Medium voltage gain and current gain
    High power gain
    Impedance
    Medium input and output impedance
    RC
    IB
    IC
    RB
    Vout
    C1
    Vin
    Q1
    IE
  • 13. Common Emitter Operation (NPN)
    Positive Half Cycle
    Vin(+)  Vb (+)  Vbe  Ib, Ic, Ie 
    VRC   Vc (+) Vout(+)
    Negative Half Cycle
    Vin(-)  Vb (+) Vbe   Ib, Ic, Ie 
    VRC   Vc (+) Vout (+)
    Output is 180° out of phase with input
    +VCC
    RC
    IB
    IC
    RB
    Vout
    C1
    Vin
    Q1
    IE
  • 14. Positive Half Cycle
    Vin(+)  Vb (+)
     Vbe  Ib, Ic, Ie 
    VRC   Vc (+) Vout(+)
    Negative Half Cycle
    Vin(-)  Vb (+)
    Vbe   Ib, Ic, Ie 
    VRC   Vc (+) Vout (+)
    Output is 180° out of phase with input
    Input and Output Graphs
    VC/ Vout
    VB
    VE/ GND
    t
    Vin
    t

×