ME 6405 Mechatronics

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

2. Contents Brief History Properties of Transistors Types of Transistors Characteristics and Applications Engineering Selection ME 6405 Transistors 0000 0010

3. History Vacuum Tube 1879 Edison Invents Light Bulb 1883 Edison 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. 1906 Lee DeForest introduced a third electrode called the grid into the vacuum tube. The resulting triodecould be used as both an amplifier and a switch. ME 6405 Transistors 0000 0011

4. Predecessors Diode Triode ME 6405 Transistors 0000 0100

5. 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) ME 6405 Transistors 0000 0101

6. 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. ME 6405 Transistors 0000 0110

7. Transistor Types BJT Bipolar Junction Transistor FET Field Effect Transistor JFET (Junction FET) MOSFET (Metal Oxide Semiconducting FET) ME 6405 Transistors 0000 0111

8. NPN bipolar junction transistor PNP bipolar junction transistor B J T s 2 types NPN (most common) When IB≠0, VCE forward biased & VBC reverse biased PNP When IB≠0, VCE reverse biased & VBC forward biased ME 6405 Transistors 0000 1000

9. npn-B J T Voltage Characteristic • Cutoff: Base-Emitter starts to conduct with VBE=0.6V • Saturation: Increasing IB causes IC to rise exponentially. • Active: • Breakdown: Ic approaches infinity due to breakdown at both junctions ME 6405 Transistors 0000 1001

10. B J T Operational Characteristics ME 6405 Transistors 0000 1010

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

12. Point of Operation • The existence of RC means that IC and VCE are no longer independent. • VCE = Vcc – IC*RC • After solving for IC, ME 6405 Transistors 0000 1100

13. Point of Operation Load-line constraint Selecting VBB and VCC, we can find the operating point, or Q point. IB = (VBB-VBE)/RB Q point for IB=100μA ME 6405 Transistors 0000 1101

14. B J T resistor sizing ß and IC,max are specified by the catalog We need to choose Values for RB and RC to keep IC and IB within specifications ME 6405 Transistors 0000 1110

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

16. FET Architecture • Enhanced MOSFET • Depleted MOSFET • JFET • Analogous BJT Terminals Nonconducting Region Conducting Region Nonconducting Region ME 6405 Transistors 0001 0000

17. NMOS Voltage Characteristic VGS < Vth IDS=0 • VDS = Constant • VGS > Vth : • 0 < VDS < VPinch off • Active Region • IDS controlled by VGS • VDS > VPinch off • Saturation Region • IDS constant Active Region Saturation Region • VDS > VBreakdown • IDS approaches IDSShort • Should be avoided ME 6405 Transistors VPinchoff 0001 0001

18. Junction Field Effect Transistor Difference from NMOS • VGS > Vth IDS=0 • VGS< -Vth : • 0 < VDS < VPinch off • Active Region • IDS controlled by VGS Saturation Region Active Region • VDS > VPinch off • Saturation Region • IDS constant • VDS > VBreakdown • IDS approaches IDSShort • Should be avoided ME 6405 Transistors VPinchoff 0001 0010

19. Transistor Selection ME 6405 Transistors 0001 0011

20. Applications of Transistors Switch Voltage Amplifier Current Amplifier ME 6405 Transistors 0001 0100

21. 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 ME 6405 Transistors 0001 0101

22. Transistor as a Voltage 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. ME 6405 Transistors 0001 0110

23. 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. ME 6405 Transistors 0001 0111

24. Example Problem Refer to your first handout ME 6405 Transistors 0001 1000

25. Questions Refer to your second handout Candy!! ME 6405 Transistors 0001 1001