1. 13 March 2014 Transistors Learning Objective To be able to describe and explain transistors. Some • Explain how a transistor can be used as a LED switch. (B+) Most All • Describe base, emitter and collector currents. (C+) • Explain what a transistor is. (C)

2. To be able to describe and explain transistors. What is a transistor and how does it work? All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

3. Transistors The transistor was the building block for all modern electronics and the foundation for microchip and computer technology. The average computer may have millions/billions of them within its circuits. Transistors are getting smaller and smaller. Intel core i7 processor contains 1.16 billion transistors. All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

4. To be able to describe and explain transistors. They can be mass-produced by the millions on a sliver of silicon. It is this ability to integrate transistors onto chips that has fueled the information age. Today these chips are not just a part of computers. They are also important in devices such as diverse as video cameras, cellular phones, copy machines, jumbo jets, modern cars, electronic scoreboards, and video games. Without the transistor there would be no Internet and no space travel. All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

5. To be able to describe and explain transistors. Some advantages are:- Lower material costs- Higher production output- Potentially faster operationSome disadvantages are:- Increased complexity in circuit design (may lead to poorer performance)- Increased engineering/R&D costs- Not serviceable after manufacture List advantages/ disadvantages of computer miniaturisation. All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

6. Explain how increasing availability of computer power requires society to make choices about acceptable uses of new technologies. Should scientists develop machines with greater artificial intelligence? http://www.youtube.com/watch?v=HwBmPiOmEGQ Are our personal freedoms under threat?

7. To be able to describe and explain transistors. Transistors video clip – additional websites are: Transistor radios www.kpsec.freeuk.com/trancirc.htm http://electronics.howstuffworks.com/transistor1.htm All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

8. To be able to describe and explain transistors. What did transistors replace? Valves Who patented the Field Effect Transistor (FET)? Julius Edgar Lilienfeld? Who came next Oskar Heil Which labs researched transistors? Bell laboratories What elements are mentioned as being used in transistors? Germanium and gold What is the difference between an NPN and a PNP transistor? The positive and negative What can they be used to measure that involves very small currents? Skin conductivity

9. To be able to describe and explain transistors. Recognise a transistor Recognise and draw the symbol for an NPN transistor and label its terminals. All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

10. The transistor as a switch Recall that the transistor is an electronic switch. It is either on or off. A small current between the base and the emitter “switches on” a much bigger current between the collector and the emitter. All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

11. To be able to describe and explain transistors. Describe base, emitter and collector currents A small base current (Ib ) is needed to switch a greater current flowing through the collector (Ic ) and emitter (Ie ). The current at the emitter is the sum of the currents in the base and the collector. Ie = Ib + Ic All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

12. To be able to describe and explain transistors. How it works as a switch Complete a labelled circuit diagram to show how an NPN transistor can be used as a switch for a light emitting diode (LED). All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)

13. To be able to describe and explain transistors. Explain why a high resistor is placed in the base circuit. The base of the transistor could be damaged if a large current flowed through it, so a resistor protects it. All – explain what a transistor is. (C) Most – describe base, collector and emitter currents. (C+) Some – explain how a transistor can be used as an LED switch. (B+)