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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.

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Chapter (3) Transistors and Integrated Circuits

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Chapter 3 transistors and integrated circuits

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

  • BJTin 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

  • Emittern-type alloyed to the base

  • The result is a pair of pn junctions separated by a base region, npn junction transistor.


Chapter 3 transistors and integrated circuits

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


Chapter 3 transistors and integrated circuits

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largeiCcurrent amplification

  • Switching operation used in digital signal processing.


Chapter 3 transistors and integrated circuits

Chapter (3)

Transistors and Integrated Circuits

  • DC Behavior

  • E forward  C reverse biased.

  • iE consist  electron across npJ holes from B.

  • g almost unity iE nearly electrons.

  • avaries from 0.90 to 0.999 where a typical value is 0.98.

iC = -aiE + ICBO

iB = -iE -iC

  • 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 generatedminority carrier ICBO


Chapter 3 transistors and integrated circuits

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 characteristicsFig.( b)similar toFig. (a)  diodecharacteristics

  • The effect of VCB small

  • +VCB  emitter open-circuited  IE = 0

  •  C section  reverse-biased junction


Chapter 3 transistors and integrated circuits

Chapter (3)

Transistors and Integrated Circuits

  • Output Characteristics

  • The collector characteristic  reverse bias diode iE = - 5 mA,  iC = - aiE@ + 5 mA.

  • The slope of the curves in Fig C due to an effective increase in aas VCB increases.

  • a alwaysless 1


Chapter 3 transistors and integrated circuits

Chapter (3)

Transistors and Integrated Circuits

The common base configuration is not good for practical current amplification


Chapter 3 transistors and integrated circuits

Chapter (3)

Transistors and Integrated Circuits


Chapter 3 transistors and integrated circuits

Chapter (3)

Transistors and Integrated Circuits

  • Input and output  CECharacteristics

  • iBdepends on VBEonly .

  • iB = 0 iC = iCEO

  • a= 0.98  b= 49,

  • A very small increase in iB large increase in iC

  • A verysmall increase in a much greater change in b.

Practice Problem 6-3


Chapter 3 transistors and integrated circuits

Chapter (3)

Transistors and Integrated Circuits


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