ELEKTRONIKOS ĮTAISAI
1
2009
Transistors
1947: W.H.Brattain and J.Bardeen (Bell Labs, USA)…
J.P.Pierce (Bell Labs): tran(sfer)+(re)sistor = transistor.
1949: W.Schockley theoretically described bipolar
junction transistor.
1956: Nobel Prize.
VGTU EF ESK
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ELEKTRONIKOS ĮTAISAI
2
2009
Transistors
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stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
3
2009
Transistors
The first transistor was invented at Bell Laboratories on December 16,
1947 by William Shockley (seated at Brattain's laboratory bench), John
Bardeen (left) and Walter Brattain (right). This was perhaps the most
important electronics event of the 20th century, as it later made possible
the integrated circuit and microprocessor that are the basis of modern
electronics.
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
4
2009
Transistors
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
5
2009
Transistors
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
6
2009
The first junction transistor
http://library.thinkquest.org/C006224/history.html
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
7
2009
History
After years of research and experimentation involving literally
hundreds of scientist from around the world, the final breakthrough
in the development of the transistor was left to three men. Dr Walter
Brattain, Dr John Bardeen and Dr William Shockley all three
scientists working at Bell laboratories, are the men credited with this
significant achievement. In December 1947 they made the historic
discovery of the transistor effect and in so doing developed the very
first transistor device. In 1956 their achievement was acknowledged
when they were awarded the Nobel Prize for physics.
http://library.thinkquest.org/C006224/history.html
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
8
2009
Transistors
Structures and symbols of (a) pnp and (b) npn transistors
Tran(sfer) + (re)sistor = Transistor
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stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
9
2009
Transistors
2.1. The structure and operation of a BJT
2.2. Basic configurations and modes of operation
2.3. Static volt-ampere characteristics of BJT
2.3.1. The Ebers-Moll representation of the BJT
2.3.2. Static volt-ampere characteristics
2.3.3. The real U-I characteristics
2.4. Two port representation of the transistor
2.5. Transistor models
2.5.1. T-type model
2.5.2. Π-type model
2.6. Transistor high frequency characteristics
2.7. Types of BJTs
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
10
2009
T
R
A
N
S
I
S
T
O
R
S
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
11
2009
Bipolar junction transistor
I E = I Ep + I En
I Ep = I Cp + I Epr
I C = I Cp + I C0
I B = I En + I Epr − I C0
... There are four important components of the currents in a BJT...
IE = IC + IB
IC ≅ IE
... The emitter current can control the output collector current...
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
12
2009
Bipolar junction transistor
DC current gain:
Α=
Α=
I Cp
IE
=
I Cp
IE
I Ep I Cp
I E I Ep
= γδ
The emitter injection efficiency, is the ratio of the hole current
injected into the base from the emitter to the total emitter-base
junction current.
The base transport factor, is the ratio of the hole current across
the collector junction to that across the emitter junction.
The DC current gain can be increased increasing the main
current and decreasing other currents.
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
13
2009
Bipolar junction transistor
Regions of operation
UCB
Configurations:
Reverseactive
• Common base (CB)
Saturation
• Common emitter (CE)
UEB
• Common collector (CC)
Cut-off
VGTU EF ESK
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Forwardactive
ELEKTRONIKOS ĮTAISAI
14
2009
T
R
A
N
S
I
S
T
O
R
S
VGTU EF ESK
CB, CE and
CC circuits
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
15
2009
Bipolar junction transistor
The ac current gain:
KI = α =
KI = α = Α + IE
KU =
d IC
d IE
I C = I Cp + I C0
dΑ
≅ Α <1
d IE
d U CB
R dI
R
= L C == α L
d U EB
rEB d I E
rEB
K P = KU K I ≅
RL
rEB
... Voltage and power amplification is possible when a BJT is in the CB
configuration.
VGTU EF ESK
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K P >> 1.
ELEKTRONIKOS ĮTAISAI
16
2009
Bipolar junction transistor
AC current gain:
KI = β =
d IC
d IC
=
=
d I B d (I E − I C )
dI C / dI E
α
=
... =
1 − dI C / dI E
1−α
β=
α
1−α
KU =
dU CE
R dI
R
= L C = L β
dU BE rBE dI B rBE
K P >> 1.
VGTU EF ESK
Amplification of AC current, voltage and
power.
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
17
2009
Bipolar junction transistor
Gain
CB
CE
KI
α<1
β>>1
>>1
KU
>>1
>>1
<1
KP
>>1
>>1
>>1
Gain properties of BJT
VGTU EF ESK
CC
stanislovas.staras@el.vgtu.lt
ELEKTRONIKOS ĮTAISAI
18
2009
Bipolar junction transistors
1. The _________ region of a BJT is thinnest, the _____________
region is the largest, and the ____________ region is the most
heavily doped.
I
2. (Electrons, Holes) are the majority carriers in the base
region of a
pnp BJT.
C
3. Which of the transistor currents is always the largest? Which is the
smallest? Which two currents are relatively close in magnitude?
4. A BJT is in its common-base configuration. Its A is 0.98 and its I C0
is 25 nA. Compute its exact value of I C when its I E is 1 mA.
5. The collector
current of an npn BJT is 2 mA, the base
current is
I
I
40 µA. Compute and approximate values of α and β.
C
C
6. If a BJT has an α of 0.98, what is its β? Find also β if α = 0.99.
Comment on the results.
VGTU EF ESK
stanislovas.staras@el.vgtu.lt
After years of research and experimentation involving literally
hundreds of scientist from around the world, the final breakthrough
in the development of the transistor was left to three men. Dr Walter
Brattain, Dr John Bardeen and Dr William Shockley all three
scientists working at Bell laboratories, are the men credited with this
significant achievement. In December 1947 they made the historic
discovery of the transistor effect and in so doing developed the very
first transistor device. In 1956 their achievement was acknowledged
when they were awarded the Nobel Prize for physics.
___trailing the Transistor History.mht