Power Electronic Devices

Clint Welch Thomas Gauci Will Scheibe Jacob Moffett Before The ● Before were implemented mercury-arc valves were used to convert AC to DC. ● Peter Cooper Hewitt invented the mercury-arc rectifiers in 1902 ● They were used to provide power for industrial motors, electric railways, streetcars, and electric locomotives, as well as for radio and for high-voltage direct current power transmission. ● A major downside to the arc valves was the large amounts of mercury used inside bulbs of fragile glass History ● In 1947, Experiments were performed at that Showed that that when two point contacts were applied to a crystal of , a signal was produced with the output power greater than the input. ● William Shockley Saw Potential in this and began to greatly expand knowledge in solid state devices. ● The first high-frequency transistor was the surface-barrier germanium transistor developed by Philco in 1953, capable of operating up to 60 MHz ● The first working transistor was developed at Bell Labs on January 26, 1954 by Morris Tanenbaum ● The first commercial silicon transistor was produced by Texas Instruments in 1954 ● The first MOS transistor actually built was by Dawon Kahng and John Atalla at Bell Labs in 1960 Where are Transistors Used ● - Small Signal Used to Control a Larger Signal Example: Microphone - Sound waves oscillate diaphragm in Mic which produces a very small current. This Voltage is applied to the gate of a transistor, and controls a larger signal going through the other two contacts.

● Switches - In a transistor, no current can flow in the collector circuit unless a current flows in the base circuit or voltage present at gate. This property allows a transistor to be used as switch. Example: Lighting Based Circuits with Light-dependent resistor (LDR). When it is placed in DARKNESS, its resistance is large. This is Placed in series with base or gate of transistor and can therefore control the current at collector-base or source-drain.

● Integrated Circuits - An (IC) consists of transistors, resistors, diodes and combined together in one -thin chip of silicon. Examples: There are IC’s available for almost any kind of function you can imagine. You can use these functions for things such as mathematical operations. This is what makes modern day processors possible.

You will find transistors in almost any modern day electronic device : Radio, Cell Phone, Keyboards, , Processors, etc.

Basic Modes of Operation

Switch

● Base current rising causes ● Property of a transistor allows emitter and collector currents to for small changes in Vin to rise exponentially produce large swings in Vout ● This causes a voltage drop between E & C [saturated] Manufacturing Technique

● Continuation of the process for making a silicon diode junction

● Repeat previous steps with the mask having a smaller opening

● Metalization could connect multiple transistors and other components into an IC Types Of Transistors Bipolar Junction (BJT) Field-Effect (FET) ● Current controlled Device ● Voltage controlled Device ● Terminals named base, emitter, and ● Terminals named gate, source, and drain collector ● No base current present, Voltage applied ● Piece of Silicon with 3 Regions to gate allows current to flow from source ● Can be PNP or NPN to drain by creating E-Field ● Commonly Used for Low-Power ● Most common modern transistor Applications ● Handles Power More Efficiently than BJT ● Cheaper to Manufacture than FET Insulated Gate Bipolar Transistor

● The IGBT combines the simple gate-drive characteristics of the with the high-current and low- saturation-voltage capability of bipolar transistors ● Similar to the cross-section of the MOSFET except the n+ drain has been replaced with a p+ layer at the collector ● Due to its capability of Fast Switching and High Efficiency it is used in many modern day devices. (VFDs, Electric cars, air conditioners, etc…) The Future of Transistors Single-atom Transistors ● Process ○ Bathed silicon in phosphene gas ○ Scanning Tunneling Microscope (STM) ○ Replaced one silicon atom in a six-atom lattice with a phosphorus atom ● Results ○ When voltage was applied across the phosphorus atom, it behaved like a transistor, switching and amplifying an electric current. ○ Showed Ohm’s Law holds on the atomic level ● Concerns ○ Can this be used to yield millions/billions of transistors? ○ Can the precise atomic spacing be maintained over larger areas? ○ Manufacturing cost and time. ○ Only operational at really cold temperatures (liquid nitrogen cold) The Future of Transistors (con’t) Graphene ● Scaled down much further than their silicon-based competitors ● Can switch much faster (300GHz compared to 12.6GHz) ● Consumes less power. References

● http://www.allaboutcircuits.com/vol_3/chpt_2/12.html ● http://fiziknota.blogspot.com/2008/09/applications-of-transistors.html ● http://en.wikipedia.org/wiki/Transistor ● http://www.differencebetween.net/technology/difference-between-bjt-and-/ ● http://www.extremetech.com/extreme/165990-scientsists-use-dna-to-shape-graphene-into-the-transistor-of-the-future ● http://spectrum.ieee.org/semiconductors/nanotechnology/a-singleatom-transistor ● http://www.sciencedaily.com/releases/2012/02/120219191244.htm ●