1. October 11, 2005ME 6405 Transistors ME 6405 Mechatronics In Order of Presentation: Jonathan Jobe David Malphurs Isaac Penny 0000 0001

2. October 11, 2005ME 6405 Transistors Contents  Brief History  Properties of Transistors  Types of Transistors  Characteristics and Applications  Engineering Selection 0000 0010

3. October 11, 2005ME 6405 Transistors History  Vacuum Tube  1879Edison Invents Light Bulb  1883Edison found that he could detect electrons flowing through the vacuum from the lighted filament to a metal plate mounted inside the bulb. “Edison Effect”  John Fleming implements Edison Effect as first diode.  1906Lee DeForest introduced a third electrode called the grid into the vacuum tube. The resulting triode could be used as both an amplifier and a switch. 0000 0011

4. October 11, 2005ME 6405 Transistors Predecessors 0000 0100 Diode Triode

5. October 11, 2005ME 6405 Transistors First Transistors  Bell Labs  1947 Invented First Transistor  Application: replace vacuum tubes  Smaller, more durable, no warm up  Made of Germanium  Current Transistors  Silicon based  Doped with phosphorus (n-type)  Doped with boron (p-type) 0000 0101

6. October 11, 2005ME 6405 Transistors The PN Junction  Forward Biasing  The external Voltage lowers the potential barrier at the junction, allowing the electrons to flow.  Reverse Biasing  The external voltage raises the potential barrier at the junction, preventing electrons from flowing. 0000 0110

7. October 11, 2005ME 6405 Transistors Transistor Types  BJTBipolar Junction Transistor  FETField Effect Transistor  JFET(Junction FET)  MOSFET (Metal Oxide Semiconducting FET) 0000 0111

8. October 11, 2005ME 6405 Transistors B J T s  2 types  NPN  (most common)  When I B ≠0, V CE forward biased & V BC reverse biased  PNP  When I B ≠0, V CE reverse biased & V BC forward biased 0000 1000 NPN bipolar junction transistor PNP bipolar junction transistor

9. October 11, 2005ME 6405 Transistors npn-B J T Voltage Characteristic Cutoff:Base-Emitter starts to conduct with V BE =0.6V Saturation: Increasing I B causes I C to rise exponentially. Active: Breakdown: I c approaches infinity due to breakdown at both junctions 0000 1001

10. October 11, 2005ME 6405 Transistors B J T Operational Characteristics Operation Region I B or V CE Char. V CE & V BE Junctions Mode CutoffI B = Very small Reverse & Reverse Open Switch SaturationV CE = SmallForward & Forward Closed Switch Active Linear V CE = Moderate Reverse & Forward Linear Amplifier Break- down V CE = LargeBeyond Limits Overload 0000 1010

11. October 11, 2005ME 6405 Transistors Equations of npn-B J T s 0000 1011 Definitions Kirchoff’s Current Law In Active region Common values for ß are 20 to 200

12. October 11, 2005ME 6405 Transistors Point of Operation 0000 1100 The existence of RC means that I C and V CE are no longer independent. V CE = V cc – I C *R C After solving for I C,

13. October 11, 2005ME 6405 Transistors Point of Operation 0000 1101 Load-line constraint Q point for I B =100μA Selecting V BB and V CC, we can find the operating point, or Q point. I B = (V BB -V BE )/R B

14. October 11, 2005ME 6405 Transistors B J T resistor sizing  ß and I C,max are specified by the catalog  We need to choose Values for R B and R C to keep I C and I B within specifications 0000 1110

15. October 11, 2005ME 6405 Transistors  Three Types of Field Effect Transistors  MOSFET (metal-oxide-semiconductor field-effect transistors)  Enhancement mode I DS α V GS  Depletion mode I DS α 1/V GS  JFET (Junction Field-effect transistors)  Available in n or p Channel  n-Channel activated by V GS > 0 for MOSFET and V GS < 0 for JFET  p-Channel activated by V GS 0 for JFET  Most Common Types  n-Channel Enhancement Mode MOSFET (NMOS)  n-Channel JFET Field Effect Transistors (FET) 0000 1111

16. October 11, 2005ME 6405 Transistors  Enhanced MOSFET  Depleted MOSFET FET Architecture BJTFET BaseGate CollectorDrain EmitterSource  JFET  Analogous BJT Terminals Conducting Region Nonconducting Region Nonconducting Region 0001 0000

17. October 11, 2005ME 6405 Transistors NMOS Voltage Characteristic Active Region Saturation Region V GS < V th I DS =0 V GS > V th : 0 < V DS < V Pinch off Active Region I DS controlled by V GS V DS > V Breakdown I DS approaches I DSShort Should be avoided V DS > V Pinch off Saturation Region I DS constant V DS = Constant V Pinchoff 0001

18. October 11, 2005ME 6405 Transistors Junction Field Effect Transistor V GS > V th I DS =0 V GS < -V th : 0 < V DS < V Pinch off Active Region I DS controlled by V GS V DS > V Pinch off Saturation Region I DS constant V DS > V Breakdown I DS approaches I DSShort Should be avoided Difference from NMOS V Pinchoff Active Region Saturation Region 0001 0010

19. October 11, 2005ME 6405 Transistors Transistor Selection 0001 0011

20. October 11, 2005ME 6405 Transistors Applications of Transistors  Switch  Voltage Amplifier  Current Amplifier 0001 0100

21. October 11, 2005ME 6405 Transistors Transistor as a Switch  Many times you just need to switch a signal on or off  Ex. Digital Logic, LED’s, PWM  Relays can perform this same function  They can usually handle higher currents than can transistors  Not Solid State, so shorter life and less durable  Slower activation time 0001 0101

22. October 11, 2005ME 6405 Transistors  Other times you want to amplify an analog signal  Ex. Sensor input, audio,  Op-amps can perform the same function  Higher gains  Can’t handle nearly as much current.  Thus Op-amps are better for signal amplification, while Transistors are better for power amplification. Transistor as a Voltage Amplifier 0001 0110

23. October 11, 2005ME 6405 Transistors Transistor as a Current Amplifier  Other times you want to amplify an analog signal  Ex. Sensor input, audio,  Op-amps can perform the same function  Higher gains  Can’t handle nearly as much current.  Thus Op-amps are better for signal amplification, while Transistors are better for power amplification. 0001 0111

24. October 11, 2005ME 6405 Transistors Example Problem  Refer to your first handout 0001 1000

25. October 11, 2005ME 6405 Transistors Questions  Refer to your second handout  Candy!! 0001 1001