Transistor history and types
- 2. KRCT
- 4. What is a Transistor? Semiconductors: ability to change from conductor to insulator Can either allow current or prohibit current to flow Useful as a switch, but also as an amplifier Essential part of many technological advances
- 6. The Transistor is Born Bell Labs (1947): Bardeen, Brattain, and Shockley Originally made of germanium Current transistors made of doped silicon
- 7. Nobel prize William Shockley ,Walter Brattain ,John Bardeen
- 8. How Transistors Work Doping: adding small amounts of other elements to create additional protons or electrons P-Type: dopants lack a fourth valence electron (Boron, Aluminum) N-Type: dopants have an additional (5th) valence electron (Phosphorus, Arsenic) Importance: Current only flows from P to N
- 9. DOPING The addition of a small amount of a different substance to a pure semiconductor crystal. The impurities give an excess of conducting electrons or an excess of conducting holes which is crucial for making a working transistor.
- 10. TYPES OF TRANSISTOR Bipolar Junction Transistor (BJT) Field-Effect Transistor (FET) Junction Field Effect Transistor (JFET) Metal Oxide Semiconductor Field Effect Transistor (MOSFET)
- 11. Junction Field Effect Transistor (JFET) The field-effect transistor (FET) controls the current between two points but does so differently than the bipolar transistor. The FET operates by the effects of an electric field. This is why the FET is sometimes called a unipolar transistor.
- 12. JFET Properties Cut-off voltage is varying for each JFET0.3V – 10V N-Channel – Negative VGS P-Channel – Positive VGS Internal Capacitance Do not Forward Bias JFET – burn out
- 13. Metal oxide semiconductor field effect transistor(MOSFET) The most common field effect transistor in both digital and analog circuits. Uses channel of n or p-type semiconductor, named NMOSFET and PMOSFET, respectively.
- 14. SILICON ON INSULATOR (SOI) For high-frequency circuits (about 5 GHz) capacitive coupling to the Si substrate limits the switching frequency. These problems are being avoided by making circuits on insulating substrates that have a thin, approximately 100 nm layer of crystalline silicon
- 15. APPLICATION In integrated circuits, the desirable properties of MOSFETs allowed them to capture nearly all market share for digital circuits. Discrete MOSFETs can be applied in transistor applications, including analog circuit.
- 16. MEDICAL APPLICATION There is great interest in constructing nano electronic devices that could detect the concentrations of bio molecules A parallel line of research seeks to create nano electronic devices which could interact with single cells for use in basic biological research. These devices are called nano sensors.
- 17. NANO MEDICINE
- 20. USING IN COMPUTER Transistors have continued to get smaller and smaller. For instance, each memory location in a computer has a pair of transistors, and there are 16 of them for each byte of memory.
- 21. COMPUTER MEMORY Normally, a junction transistor is "off" when there is no base current and switches to "on" when the base current flows. That means it takes an electric current to switch the transistor on or off. This kind of arrangement is known as a flip-flop
- 22. ADVANTAGE & LIMITATION ADVANTAGE; Lower power dissipation and generally greater energy efficiency. Low operating voltages compatible with batteries of only a few cells LIMITATION; Silicon transistors can age and fail Sensitivity to radiation and cosmic rays
Editor's Notes
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