chapter (3) transistors and integrated circuits
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Chapter (3) Transistors and Integrated Circuits. B I P O L A R J U N C T I O N T R A N S I S T O R. BJT in contrast to the "unipolar " FET Both minority and majority carries play significant roles. Permits greater gain better high-frequency performance. Alloy Structure consist of. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter (3)Transistors and Integrated Circuits
B I P O L A R J U N C T I O N T R A N S I S T O R
BJT in contrast to the "unipolar" FET
• Both minority and majority carries play significant roles.• Permits greater gain better high-frequency performance.
Alloy Structure consist of
• Collector (C) n-type chip less than 1 mm square• Base (B) p-type thinner than this paper• Emitter n-type alloyed to the base • The result is a pair of pn junctions separated by a base
region, npn junction transistor.
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Chapter (3)Transistors and Integrated Circuits
Planar Structure
npn BJT• (n) grown upon a heavily doped (n+) substrate.• oxidation of the surface • window opened to diffuse impurities
(P) into the crystal to form the pn junction.• A smaller window for emitter in opened to diffuse emitter region (n).
Biasing Parameters
BJT C E B VEB VCB iE iC iB
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Chapter (3)Transistors and Integrated Circuits
Operation• The emitter junction forward biased
VEB reduced the barrier at emitter electrons injection into B where they are
minority carriers.• The collector junction is reverse biased
VCB increase the barrier at C
• B is very thin most electron pass from E to C
• The net result transfer electron from E to C.• Large RL insertion in C large voltage
voltage amplification • Variation of the base current iB large iC
current amplification • Switching operation used in digital signal
processing.
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Chapter (3)Transistors and Integrated Circuits
DC Behavior• E forward C reverse biased. • iE consist electron across
np J holes from B.
• almost unity iE nearly electrons.• varies from 0.90 to 0.999 where a typical value is 0.98.• Most of these electrons in B
diffuse to C B is very narrow. • iC consist of iE and a very small current due to thermally generated minority carrier ICBO CBO
KTevCBO IeI 1/
iC = -iE + ICBO
iB = -iE -iC
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Chapter (3)Transistors and Integrated Circuits
Common - Base Characteristics
• CB configuration
• B common input E output C.
• The emitter-base section forward-biased
diode.
Input Characteristics
• Input characteristics Fig.( b ) similar to
Fig. (a) diode characteristics
• The effect of VCB small
• +VCB emitter open-circuited IE = 0
C section reverse-biased junction
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Chapter (3)Transistors and Integrated Circuits
Output Characteristics
• The collector
characteristic reverse
bias diode iE = - 5 mA,
iC = - iE + 5 mA.
• The slope of the curves
in Fig C due to an
effective increase in
as VCB increases.
• always less 1
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The common base
configuration is not good for
practical current amplification
Chapter (3)Transistors and Integrated Circuits
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Chapter (3)Transistors and Integrated Circuits
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Chapter (3)Transistors and Integrated Circuits
Input and output CE Characteristics
iB depends on VBE only .
iB = 0 iC = iCEO
= 0.98 = 49,
A very small increase in iB large
increase in iC
A very small increase in much
greater change in .Practice Problem 6-3
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Chapter (3)Transistors and Integrated Circuits