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Electronic Circuit
CH. 4 Bipolar Junction Transister
Dept. of Electrical and Electronic Engineering
Chang Bum, Lee
Office: 1315
(055)380-9243
[email protected]
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Bipolar Junction Transistors
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Contents
1.History of BJT
2.First BJT
3.Basic symbols and features
4.A little bit of physics…
5.Currents in BJT’
6.Basic configurations
7.Characteristics
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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.
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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.
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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.
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Point-Contact Transistor –
-first transistor ever made
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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
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Understanding of BJT
COLLECTER




EMITTER
force
voltage/current
water flow
Current amplification
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Basic models of BJT
 npn transistor
 Diode
 Diode
 pnp transistor
 Diode
 Diode
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Qualitative basic operation of BJTs
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Basic models of BJT
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BJTs – Basic Configurations(2)
 Fluid Flow Analogy
 Technology of BJTs
 pnp BJT
 npn BJT
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FET Transistors(1)
 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
FET Transistors(2)
 In practice the body and
source leads are almost
always connected
 Most packages have these
leads already connected
– Circuit Symbols
MOSFET
-D
-D
-B
-G
-G
-S
-B
-S
JFET
-D
-G
-S
BJTs – Practical Aspects
Heat sink
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BJTs – Testing
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