Chapter 3: Islamic University of Gaza Bipolar Junction...
Transcript of Chapter 3: Islamic University of Gaza Bipolar Junction...
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Chapter 3:
Bipolar Junction Transistors
Islamic University of Gaza
Dr. Talal Skaik
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Copyright ©2009 by Pearson Education, Inc.
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Common–Emitter Configuration
•The emitter is common to both input (base-emitter) and output (collector-
emitter).
•The input is on the base and the output is on the collector.
2 Dr. Talal Skaik 2014
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Common-Emitter Characteristics
3 Dr. Talal Skaik 2014
(a) collector characteristics; (b) base characteristics.
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Common-Emitter Amplifier Currents
IC = IE + ICBO
When IB = 0 A the transistor is in cutoff, but there is some
minority current flowing called ICEO.
B
B
1 1
I =0, and take 0.996,
(0 A)250
1 1 0.996 1 0.996 0.004
If were 1 A, the resulting collector current with I =0 A would
be 250(1 A) =0.25 mA, as reflect
CBOBC
CBO CBO CBOC CBO
CBO
III
For
I I II I
I
ed in the characterestics.
where ICBO = minority collector current
4
ICBO is usually so small that it can be ignored, except in high
power transistors and in high temperature environments.
Dr. Talal Skaik 2014
Since IE = IC + IB , IC = (IC + IB ) + ICBO
0 μA1 B
CBOCEO I
II
α
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Beta ()
In DC mode:
In AC mode:
represents the amplification factor of a transistor. ( is sometimes
referred to as hfe, a term used in transistor modeling calculations)
B
C
I
Iβ dc
constantac
CEVB
C
I
I
5 Dr. Talal Skaik 2014
For practical devices is typically 50 to over 400.
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Determining from a Graph
Beta ()
108
A 25
mA 2.7β 7.5VDC CE
100
μA 10
mA 1
μA) 20 μA (30
mA) 2.2mA (3.2β
7.5V
AC
CE
6
ac and dc are usually reasonably close and are often used
interchangeably.
Dr. Talal Skaik 2014
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Relationship between amplification factors and :-
1β
βα
1α
αβ
Beta ()
Relationship Between Currents
BC βII BE 1)I(βI
7
using ,
1 1 1
( 1)
C C
B E
E C B
C CC
I I
I I
and I I I
I II
, = ,E C B B BI I I I I
Dr. Talal Skaik 2014
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Biasing
8 Dr. Talal Skaik 2014
Determining the proper biasing arrangement for a common-emitter
npn transistor configuration.
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Common–Collector Configuration The input is on the base and the output is on the emitter.
9 Dr. Talal Skaik 2014
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Common–Collector Configuration The characteristics are similar to those of the common-emitter
configuration, except the vertical axis is IE.
10 Dr. Talal Skaik 2014
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
Transistor Testing
• DMM
Some DMMs measure DC or hFE.
• Ohmmeter
11
Checking the forward-biased base-to-
emitter junction of an npn transistor.
Checking the reverse-biased base-to-
collector junction of an npn transistor.
Dr. Talal Skaik 2014
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Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky
12
Various types of general-purpose or switching transistors:
(a) low power; (b) medium power; (c) medium to high power.
Dr. Talal Skaik 2014