Electronic Circuit CH. 4 Bipolar Junction Transister Dept. of Electrical and Electronic Engineering Chang Bum, Lee Office: 1315 (055)380-9243 cblee@ysu.ac.kr

Bipolar Junction Transistors 2

Contents History of BJT First BJT Basic symbols and features A little bit of physics… Currents in BJT’ Basic configurations Characteristics 3

First - BJTs The transistor was probably the most important invention of the 20th Century, and the story behind the invention is one of clashing egos and top secret research.  Reference: Bell Labs Museum B. G. Streetman & S. Banerjee ‘Solid State Electronic Devices’, Prentice Hall 1999. 4

Interesting story(1) Picture shows the workbench of John Bardeen (Stocker Professor at OU) and Walter Brattain at Bell Laboratories. They were supposed to be doing fundamental research about crystal surfaces. The experimental results hadn't been very good, though, and there's a rumor that their boss, William Shockley, came near to canceling the project.  But in 1947, working alone, they switched to using tremendously pure materials.  It dawned on them that they could build the circuit in the picture. It was a working amplifier!  John and Walter submitted a patent for the first working point contact transistor.  5

Interesting story(2) Shockley was furious and took their work and invented the junction transistor and submitted a patent for it 9 days later. The three shared a Nobel Prize in 1955. Bardeen and Brattain continued in research (and Bardeen later won another Nobel). Shockley quit to start a semiconductor company in Palo Alto. It folded, but its staff went on to invent the integrated circuit (the "chip") and to found Intel Corporation. By 1960, all important computers used transistors for logic, and ferrite cores for memory. 6

Point-Contact Transistor – first transistor ever made 7

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First Bipolar Junction Transistors W. Shockley invented the p-n junction transistor The physically relevant region is moved to the bulk of the material 9

Understanding of BJT force voltage/current water flow COLLECTER EMITTER force voltage/current water flow Current amplification 10

Basic models of BJT npn transistor Diode Diode pnp transistor Diode 11

Qualitative basic operation of BJTs 12

Basic models of BJT 13

BJTs – Basic Configurations(2) Fluid Flow Analogy Technology of BJTs pnp BJT npn BJT 14

FET Transistors(1) BJT FET Analogous to BJT Transistors Output is controlled by input voltage rather than by current 4 Pins vs. 3 BJT FET Collector Drain Base Gate Emitter Source N/A Body Spring 2007 Slides Voltage controlled – hence “field effect” 15

FET Transistors(2) – Circuit Symbols In practice the body and source leads are almost always connected Most packages have these leads already connected MOSFET B S G D B S G D JFET Spring 2007 Slides S G D 16

BJTs – Practical Aspects Heat sink 17

BJTs – Testing 18