introduction to bjt amplifier bjt (review). still remember about bjt? the emitter current (i e ) is...
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![Page 1: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/1.jpg)
Introduction to BJT Amplifier
BJT (Review)
![Page 2: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/2.jpg)
Still remember about BJT?
CBE III
The emitter current (iE) is the sum of the collector current (iC) and the base current (iB)
iB << iE and iC OTHER PRAMETERS &
EQUATIONS?
CBE iii
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BJT
Basic structure and schematic symbol
E C
B
E
B
C
n npE C
B
E C
B
E
B
C
p pnE C
B
npn type pnp type
approximate equivalents
transistorsymbols
![Page 4: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/4.jpg)
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Common-emitter current gain, β Range: 50 < β < 300
Common-base current gain, α Range: always slightly
less than 1 The current relationship
between these 2 parameters are as follows:
EC
EC
CE
BE
BC
BCE
ii
ii
ii
ii
ii
iii
1
1
1
1
But
)(
)(
![Page 5: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/5.jpg)
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BJT as amplifying device B-E junction is forward-biased B-C junction is reverse-biased
![Page 6: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/6.jpg)
BIASING OF BJT
Remember…! for normal operation
emitter-base junction is always forward-biased
AND
collector-base junction is always reverse-biased
![Page 7: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/7.jpg)
FORWARD BIASING E/B JUNCTION
![Page 8: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/8.jpg)
REVERSE BIASING C/B JUNCTION
![Page 9: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/9.jpg)
BIASING NPN TRANSISTOR
![Page 10: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/10.jpg)
Common-Emitter Circuit
(a) with an npn transistor
(b) with a pnp transistor
(c) with a pnp transistor biased with a positive voltage source
![Page 11: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/11.jpg)
DC Analysis - Common-Emitter Circuit
Transistor current-voltage characteristics of the common-emitter circuit
![Page 12: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/12.jpg)
DC Analysis - Common-Emitter Circuit
Common-emitter circuit with an npn transistor
Common-emitter dc equivalent circuit, with piecewise linear parameters
![Page 13: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/13.jpg)
DC Analysis - Common-Emitter Circuit
B
BEBBB R
onVVI
)(
Look for calculation examples in Neamen (Chapter 3), Example 3.3 & 3.4
Usually VBE(on) = 0.7 V
CCCCCE
CECCCC
BC
RIVV
VRIV
II
or
Common-emitter dc equivalent circuit
![Page 14: Introduction to BJT Amplifier BJT (Review). Still remember about BJT? The emitter current (i E ) is the sum of the collector current (i C ) and the base](https://reader036.vdocuments.net/reader036/viewer/2022062301/56649f345503460f94c51422/html5/thumbnails/14.jpg)
DC Analysis - Load Line & Modes of Operation
Base-emitter junction characteristics and the input load line
BQB
BEBBB I
R
VVI
Base on Figure A, using KVL around B-E loop:
Figure A
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Base on Figure A, 2 end points of the load line are found by setting IC = 0
So, VCE = VCC = 10 VWhen VCE = 0,IC = VCC/RC = 5 mA
IBQ is the value from the previous slide = 15 µASo, ICQ = βIBQ
If β = 200, ICQ = 3000 µA = 3 mA
So, VEQ = 4 V
DC Analysis - Load Line & Modes of Operation
CECCCC VRIV
CCQCCCEQ RIVV
Common- emitter transistor characteristics and the collector-emitter load line
CECCCC VRIV
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BJT as an Amplifier
• Amplification of a small ac voltage by placing the ac signal source in the base circuit
• Vin is superimposed on the DC bias voltage VBB by connecting them in series with base resistor RB:
• Small changes in the base current circuit causes large changes in collector current circuit
BDCC II
END