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(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 #23EE130 Lecture 23, Slide 1

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

Output Characteristics for Common-Emitter Configuration

EE130 Lecture 23, Slide 3

Modes of Operation

Common-emitter output characteristics

(ICvs.VCE)

EE130 Lecture 23, Slide 4

*or not strongly forward biased

BJT Electrostatics

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

EE130 Lecture 23, Slide 5

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

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

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)

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

- 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

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