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ME 6405 Student Lecture Transistor Sung-bum Kang Keun Jae Kim Hongchul Sohn Wenwei Xu October 1, 2009 Georgia Institute of Technology.

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Presentation on theme: "ME 6405 Student Lecture Transistor Sung-bum Kang Keun Jae Kim Hongchul Sohn Wenwei Xu October 1, 2009 Georgia Institute of Technology."— Presentation transcript:

1 ME 6405 Student Lecture Transistor Sung-bum Kang Keun Jae Kim Hongchul Sohn Wenwei Xu October 1, 2009 Georgia Institute of Technology

2 Contents Introduction to Transistor (Speaker: Sung-bum Kang) Field Effect Transistor (Speaker: Hongchul Sohn) Power Transistor (Speaker: Wenwei Xu) Applications of Transistor (Speaker: Wenwei Xu) 5 Bipolar Junction Transistor (Speaker: Keun Jae Kim) 2

3 Transistor Part 1 Introduction to Transistor (Speaker: Sung-bum Kang) 1 Field Effect Transistor (Speaker: Hongchul Sohn) Power Transistor (Speaker: Wenwei Xu) 3 4 Applications of Transistor (Speaker: Wenwei Xu) 5 Bipolar Junction Transistor (Speaker: Keun Jae Kim) 2

4 Introduction Question #1: How can we transfer original signal in long distance without loss? Amplifier and Electronic Switch are needed. Amplifier: any device that changes, usually increases, the amplitude of a signal. Electronic Switch: switch that the physical opening and closing is achieved by applying appropriate electrical control signals. Question #2: How can we control the TV with remote-controller? Question #3: How can a computer recognize 0(off) and 1(on) for computing?

5 Introduction Early 20 th century, vacuum tube was used for the amplifier and switch. ENIAC, the first general-purpose electronic computer, contains 17,468 vacuum tubes. Vacuum Tube Radio However, Vacuum Tube is too big, fragile, and energy-consuming. Transistor solved this problem.

6 Introduction – Invention of Transistor Invention In 1947, John Bardeen, Walter Brattain, and William Schockly, researchers at Bell Lab, invented Transistor. They found Transistor Effect: when electrical contacts were applied to a crystal of germanium, the output power was larger than the input. In 1956, they were awarded the Nobel Prize in physics. Transistor is a semiconductor device commonly used to amplify or switch electronic signals. John Bardeen, Walter Brattain, and William Schockly First model of Transistor, 1947

7 Introduction – Progress of Transistor more than 2.9 billion transistors is packed into an area of fingernail 1941, Vacuum Tube 1948, the first (Germanium) TR 1954, Silicon TR 1958, Integrated Circuit Sep 2009, 22nm silicon wafer Now? Edison effect John Bardeen, Walter Brattain, and William Schockly At TI Lab, Ease of processing, lower cost, greater power handling, more stable temperature characteristics Intel CEO Paul Otellini, Sep Individual electronic components were soldered on to printed circuit boards. IC placed all components in one chip.

8 Introduction – Underlying Science Semiconductor is a basic building material of most integrated circuits. is a material that has an electrical resistivity between that of a conductor and an insulator. has a few charge carriers(holes or free electrons) and may hence be classified as almost insulator. However, the conductivity increases by adding impurities(doping). Silicon is used in most commercial semiconductors

9 Introduction – Underlying Science Doping P(positive)-type doping is adding a certain type of atoms to the semiconductor in order to increase holes. P-type semiconductor, acceptor N(negative)-type doping is adding some amount of an element with more electrons in order to increase free electrons. N-type semiconductor, donor Add Group III(Boron)Add Group V (Phosphorous)

10 Introduction – Underlying Science PN Junction is a junction formed by P-type and N-type semiconductors together in very close contact. Electrons(+) from n(-) region diffuse to occupy holes(-) in p(+) region. Thin depletion region forms near junction. What happens at the junction?

11 Introduction – Underlying Science Forward bias -V pumps electrons into the N-region. +V pumps more holes into the P-region. Excess of charge in P and N region will apply pressure on the depletion region and will make it shrink. current flows Backward bias -V sucked out electrons from N-region. +V sucked out holes from P-region. The depletion layer widens and it occupies the entire diode(p-n). current doesnt flow External Energy

12 Introduction – Types of Transistor Transistor are categorized by Semiconductor material: germanium, silicon, gallium arsenide, etc. Structure: BJT, FET, IGFET (MOSFET), IGBT Polarity: NPN, PNP (BJTs); N-channel, P-channel (FETs) Maximum power rating: low, medium, high Maximum operating frequency: low, medium, high Application: switch, audio, high voltage, etc. Physical packaging: through hole, surface mount, ball grid array, etc. Amplification factor Various Types of Transistor: General Purpose Transistors Bipolar Junction Transistor (BJT) Field Effect Transistors (FET) Power Transistors

13 Transistor Part 2 Field Effect Transistor (Speaker: Hongchul Sohn) Power Transistor (Speaker: Wenwei Xu) 3 4 Applications of Transistor (Speaker: Wenwei Xu) 5 Bipolar Junction Transistor (Speaker: Keun Jae Kim) Introduction to Transistor (Speaker: Sung-bum Kang) 1 2

14 BJT Introduction PNP NPN 3 Terminals Base (B) Collector (C) Emitter (E) 2 Types: NPN, PNP Currents flow in opposite direction NPN: BE forward biased BC reverse biased PNP: BE reverse biased BC forward biased

15 Georgia Institute of Technology15 BJT Characteristics I C is controlled by I B (Current Control) β (beta) is amplification factor for transistor Typical value of is β 20 ~ 200 i E = i C + i B i C = βi B V BE = V B – V E V CE = V C - V E

16 Operating Regions BJT Operating Regions

17 Operating Regions Operating RegionParametersMode Cut Off V BE < V cut-in V CE > V supply I B = I C = 0 Switch OFF Linear V BE = V cut-in V sat < V CE < V supply I C = β*I B Amplification Saturated V BE = V cut-in, V CE < V sat I B > I C,max, I C,max > 0 Switch ON BJT Operating Regions

18 Georgia Institute of Technology18 1)Cutoff Region: V BE V supply 2)Active / Linear Region: V BE = V cut-in, i B > 0 i C = βi B, V sat < V CE < V supply 3)Saturation Region: V BE = V cut-in, i B > i C,max i C,max, V CE < V sat V in V supply BJT Operating Regions

19 V Supply V in RBRB RCRC Question: What is the minimum V in that can use the transistor as an amplifier? Given: R B = 10 kΩ R C = 1 kΩ β = 100 V Supply = 10 V V cut-in = 0.7 V V sat = 0.2 V i B = i C / β = /100 = 0.098mA BJT as Amplifier V in - i B *R B – V BE = 0 V supply – i C *R C – V CE =0 i C = (V supply – V CE ) / R C Set V CE = V sat = 0.2V i C = (10 – 0.2) / 1000 = 9.8mA i C = βi B V in = i B *R B + V BE Set V BE = V cut-in = 0.7V V in = 0.098*(10 -3 )* V V in = 1.68V or greater.

20 From 3 rd Exercise Turns on/off coils digitally BJT as Switch

21 Introduction to Transistor (Speaker: Sung-bum Kang) Field Effect Transistor (Speaker: Hongchul Sohn) Power Transistor (Speaker: Wenwei Xu) Applications of Transistor (Speaker: Wenwei Xu) Bipolar Junction Transistor (Speaker: Keun Jae Kim) Transistor Part 3

22 Field-Effect Transistors Basics Conduction of a channel is controlled by electric field effect Three terminals: gate, source, drain Voltage-controlled current device control terminal current channel of charge carriers for charge carriers control voltage Very little current flows through input (gate) terminals

23 Field-Effect Transistors BJT vs. FET What was BJT then? A current-controlled current device Comparison BJTFET Input current controls output current Input voltage controls output current BaseGate CollectorDrain EmitterSource

24 Field-Effect Transistors Types JFET (Junction FET) MOSFET (Metal-oxide-semiconductor FET) MESFET (Metal-semiconductor FET) HFET (Hetero-structure FET) MODFET (Modulation doped FET) IGBT (Insulated-gate bipolar transistor) Power MOSFETs FREDFET (Fast reverse or fast recovery epitaxial diode FET) ISFET (Ion-sensitive FET) DNAFET JFET (Junction FET) MOSFET (Metal-oxide-semiconductor FET)

25 JFETs n-channel General Properties Advantages: Much higher input resistance, lower noise, easier fabrication, ability to handle higher currents and powers Disadvantages: Slower speeds in switching circuits, smaller bandwidth for a given gain in an amplifier p-channel

26 n-channel JFET Characteristics

27 n-channel JFET Characteristics Idealized Static

28 n-channel JFET Characteristics Practical Static Transfer

29 MOSFETs MOSFETs or Insulated-gate FET (IGFET) n-channel Enhancement General Properties Input resistance even higher Used primarily in digital electronic circuits Provide controlled-source characteristics in amplifier circuits n-channel Depletion

30 n-channel Enhancement MOSFET Characteristics

31 n-channel Enhancement MOSFET Characteristics Practical

32 n-channel Depletion MOSFET Characteristics Practical

33 Task: Design a n-channel common-source JFET Amplifier Amplifiers, Switches Applications You CAN do it!! Psst! You can read it!!

34 Transistor Part 4 Introduction to Transistor (Speaker: Sung-bum Kang) Field Effect Transistor (Speaker: Hongchul Sohn) Power Transistor (Speaker: Wenwei Xu) 1 3 Applications of Transistor (Speaker: Wenwei Xu) Bipolar Junction Transistor (Speaker: Keun Jae Kim) 2 4 5

35 Power Transistor Concerned with delivering high power Used in high voltage and high current application In general Fabrication process different in order to: Dissipate more heat Avoid breakdown Lower gain than signal level transistor

36 Power BJT Same structure to the signal level BJT The active area is distinctively higher-high current capacity Thick and low-doped collector region Large heat dissipation--- larger dimensions

37 Power MOSFET Same working principles to MOSFET Designed to handle large power Low internal voltage drop and high current capacity High commutation speed and good efficiency at low voltageshigh speed switch

38 Applications of Transistor building blocks for modern electronics Digital logic circuits Microprocessors, microcontrollers, chips (TTL) Photo-transistors Replaces normal switches, mechanical relays. A/D converter Encoders Multiplexers Power supplies more … microprocessor wireless communication motor headphone, microphone

39 Applications(cont.) – Switch for a digital signal: BJT or MOSFET – Switch for a analog signal: JFET – Switch for a power signal: Power MOSFET or BJT – Current controlled-current amplifier: BJT – Voltage controlled-current amplifier: JFET or MOSFET Transistor applications Switch Amplifier

40 Small input voltage and large output current operated in the cut-off region(open) and saturation region(close) Example: 2N3904 NPN Assuming LED requires mA to provide a bright display and has 2 voltage drop when forwarded biased Output=0Voff Output=5V---on, the transistor is in saturation, with base current Collector current (LED current) is limited by collector resistor BJT as switches

41 BJT as amplifiers Audio amplifiers, radio frequency amplifiers, regulated power supplies Low input impedance and high voltage gain Example Speaker amplifier BJT series produce higher gain

42 Applications of FET Advantages of FET over BJT They are devices controlled by voltage with a very high input impedance (10 7 to ohms) FETs generate a lower noise level than the Bipolar Junction Transistor (BJT) FETs are more stable than BJT with temperature FETs are easier to manufacture than the BJT, because they require fewer steps to be built and they allow more integrated devices in the same IC FETs behave like resistors controlled by voltage for small drain- source voltage values The high input impedance of FET allows them to withhold loads long enough to allow its usage as storage elements Power FETs can dissipate higher power and can switch very large currents.

43 Applications of FET Amplifiers Small Signal Low Distortion High Gain Low Noise amplifier Selectivity High-Frequency Switches Chopper-Type Analog Gate Communicator Protection Diodes Low-leakage Current Limiters Resistors Mixers Oscillators

44 FET as analog switch-example When V GS = 0, FET becomes saturated and it behaves like a small resistance(<100 ohm) and, therefore, V OUT = {R DS / (R D + R DS (ON) )}* V in R D >>R DS, V OUT 0 When a negative voltage equal to V GS (OFF) is applied to the gate, the FET operates in the cut-off region and it acts like a very high resistance usually of some mega ohms. Hence output voltage becomes nearly equal to input voltage.

45 Contact information (in order of presenting) Sung-bum Keun Jae Hongchul Wenwei

46 References Introduction to Electrical Engineering, Mulukata S. Sarma, Oxford University Press, 2001, Chap. 7.4~8.4. Fall 2008 Transistors Slides Introduction to Electrical Engineering, Mulukata S. Sarma, Oxford University Press, 2001, Chap. 7.4~8.4. Fall 2008 Transistors Slides

47 Thank you!


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