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QUIZ #3 Results (undergraduate scores only, N = 39) Mean = 22.1; Median = 22; Std. Dev. = 1.995 High = 25; Low = 18 OUTLINE The Bipolar Junction Transistor Fundamentals Ideal Transistor Analysis Reading: Chapter 10, 11.1. Lecture #23. Base Current Components (Active Bias).

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Lecture 23

QUIZ #3 Results

(undergraduate scores only, N = 39)

Mean = 22.1; Median = 22; Std. Dev. = 1.995

High = 25; Low = 18

OUTLINE

The Bipolar Junction Transistor

Fundamentals

Ideal Transistor Analysis

Reading: Chapter 10, 11.1

Lecture #23

EE130 Lecture 23, Slide 1


Base current components active bias
Base Current Components (Active Bias)

The base current consists of majority carriers supplied for

  • Recombination of injected minority carriers in the base

  • Injection of carriers into the emitter

  • Reverse saturation current in collector junction

    • Reduces | IB |

  • Recombination in the base-emitter depletion region

EMITTER

COLLECTOR

BASE

n-type

p-type

p-type

EE130 Lecture 23, Slide 2


Circuit configurations
Circuit Configurations

Output Characteristics for Common-Emitter Configuration

EE130 Lecture 23, Slide 3


Modes of operation
Modes of Operation

Common-emitter output characteristics

(ICvs.VCE)

EE130 Lecture 23, Slide 4

*or not strongly forward biased


Bjt electrostatics
BJT Electrostatics

  • Under normal operating conditions, the BJT may be viewed electrostatically as two independent pn junctions

EE130 Lecture 23, Slide 5


Electrostatic potential, V(x)

Electric field, e(x)

Charge density, r(x)

EE130 Lecture 23, Slide 6


Bjt performance parameters pnp

Emitter Efficiency:

Decrease (5) relative to (1+2) to increase efficiency

BJT Performance Parameters (PNP)

  • Base Transport Factor:

    • Decrease (1) relative to (2) to increase transport factor

  • Common-Base d.c. Current Gain:

EE130 Lecture 23, Slide 7


Collector current pnp

The collector current is comprised of

Holes injected from emitter,

which do not recombine in the base  (2)

Reverse saturation current of collector junction  (3)

where ICB0 is the collector current

which flows when IE = 0

Collector Current (PNP)

  • Common-Emitter d.c. Current Gain:

EE130 Lecture 23, Slide 8


Summary bjt fundamentals
Summary: BJT Fundamentals

IE = IB + IC

  • Notation & conventions:

  • Electrostatics:

    • Under normal operating conditions, the BJT may be viewed electrostatically as two independent pn junctions

pnp BJT

npn BJT

EE130 Lecture 23, Slide 9


  • Performance parameters:

    • Emitter efficiency

    • Base transport factor

    • Common base d.c. current gain

    • Common emitter d.c. current gain

EE130 Lecture 23, Slide 10


Notation pnp bjt
Notation (PNP BJT)

NE = NAE

DE = DN

tE = tn

LE = LN

nE0 = np0 = ni2/NE

NB = NDB

DB = DP

tB = tp

LB = LP

pB0 = pn0 = ni2/NB

NC = NAC

DC = DN

tC = tn

LC = LN

nC0 = np0 = ni2/NC

EE130 Lecture 23, Slide 11


Ideal transistor analysis
Ideal Transistor Analysis

  • Solve the minority-carrier diffusion equation in each quasi-neutral region to obtain excess minority-carrier profiles

    • different set of boundary conditions for each region

  • Evaluate minority-carrier diffusion currents at edges of depletion regions

  • Add hole & electron components together  terminal currents

EE130 Lecture 23, Slide 12


Emitter region formulation

Diffusion equation:

Boundary Conditions:

Emitter Region Formulation

EE130 Lecture 23, Slide 13


Base region formulation

Diffusion equation:

Boundary Conditions:

Base Region Formulation

EE130 Lecture 23, Slide 14


Collector region formulation

Diffusion equation:

Boundary Conditions:

Collector Region Formulation

EE130 Lecture 23, Slide 15


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