transistors 1947: w.h.brattain and j.bardeen (bell labs ... 1.pdf · transistors 1947: w.h.brattain...

ELEKTRONIKOS ĮTAISAI 2009

VGTU EF ESK [email protected]

1

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.



2

Transistors



3

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.

Transistors



4

Transistors



5

Transistors



6

The first junction transistor

http://library.thinkquest.org/C006224/history.html



7

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.

History

http://library.thinkquest.org/C006224/history.html



8

Structures and symbols of (a) pnp and (b) npn transistors

Transistors

Tran(sfer) + (re)sistor = Transistor



9

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



10

T

R

A

N

S

I

S

T

O

R

S



11

EnEpE III +=

EprCpEp III +=

C0CpC III +=

C0EprEnB IIII −+=

... There are four important components of the currents in a BJT...

BCE III += EC II ≅

... The emitter current can control the output collector current...

Bipolar junction transistor



12

E

Cp

I

I=Α

γδΑ ===Ep

Cp

E

Ep

E

Cp

I

I

I

I

I

I

DC current gain:

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.




13

Saturation

Forward-

active Cut-off

Reverse-

active

UCB

UEB

Configurations:

• Common base (CB)

• Common emitter (CE)

• Common collector (CC)

Regions of operation




14

T

R

A

N

S

I

S

T

O

R

S

CB, CE and

CC circuits



15

E

C

d

d

I

IK I ==α

1d

d

EE <≅+== Α

ΑΑα

IIK I

EB

L

EEB

CL

EB

CB

d

d

d

d

r

R

Ir

IR

U

UKU α====

C0CpC III +=

EB

L

r

RKKK IUP ≅=

The ac current gain:

... Voltage and power amplification is possible when a BJT is in the CB

configuration.




16.1>>PK

( )

α

α

β

−=

−=

=−

===

1...

d/d1

d/d

d

d

d

d

EC

EC

CE

C

B

C

II

II

II

I

I

IK I

βBE

L

BBE

CL

BE

CE

d

d

d

d

r

R

Ir

IR

U

UKU ===

AC current gain:

.1>>PK

α

αβ

−=

1

Amplification of AC current, voltage and

power.




17

Gain properties of BJT

>>1>>1>>1KP

<1>>1>>1KU

>>1β>>1α<1KI

CCCECBGain




18

1. The _________ region of a BJT is thinnest, the _____________

region is the largest, and the ____________ region is the most

heavily doped.

2. (Electrons, Holes) are the majority carriers in the base region of a

pnp BJT.

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

is 25 nA. Compute its exact value of when its is 1 mA.

5. The collector current of an npn BJT is 2 mA, the base current is

40 µA. Compute and approximate values of α and β.

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.

CI

CI

C0I

CI EI

CI

Bipolar junction transistors

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

transistors 1947: w.h.brattain and j.bardeen (bell labs ... 1.pdf · transistors 1947: w.h.brattain...

Documents