Neamen Microelectronics, 4eChapter 5-1

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Microelectronics Circuit Analysis and Design

Donald A. Neamen

Chapter 5

The Bipolar Junction Transistor

Neamen Microelectronics, 4eChapter 5-2

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In this chapter, we will:

Discuss the physical structure and operation of the bipolar junction transistor.

Understand the dc analysis and design techniques of bipolar transistor circuits.

Examine three basic applications of bipolar transistor circuits.

Investigate various dc biasing schemes of bipolar transistor circuits, including integrated circuit biasing.

Consider the dc biasing of multistage or multi-transistor circuits.

Neamen Microelectronics, 4eChapter 5-3

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Cross Section of Integrated Circuit npn Transistor

Neamen Microelectronics, 4eChapter 5-4

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Modes of Operation

Forward-ActiveB-E junction is forward biasedB-C junction is reverse biased

SaturationB-E and B-C junctions are forward biased

Cut-OffB-E and B-C junctions are reverse biased

Inverse-Active (or Reverse-Active)B-E junction is reverse biasedB-C junction is forward biased

Neamen Microelectronics, 4eChapter 5-5

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npn BJT in Forward-Active

Neamen Microelectronics, 4eChapter 5-6

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Electrons and Holes in npn BJT

Neamen Microelectronics, 4eChapter 5-7

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Electrons and Holes in pnp BJT

Neamen Microelectronics, 4eChapter 5-8

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Circuit Symbols and Current Conventions

Neamen Microelectronics, 4eChapter 5-9

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Current Relationships

1

)1(

EC

BE

BC

BCE

ii

ii

ii

iii

Neamen Microelectronics, 4eChapter 5-10

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Common-Emitter Configurations

Neamen Microelectronics, 4eChapter 5-11

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Common-Base Configuration

Neamen Microelectronics, 4eChapter 5-12

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Current-Voltage Characteristics of a Common-Base Circuit

Neamen Microelectronics, 4eChapter 5-13

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Current-Voltage Characteristics of a Common-Emitter Circuit

Neamen Microelectronics, 4eChapter 5-14

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Early Voltage/Finite Output Resistance

Neamen Microelectronics, 4eChapter 5-15

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Effects of Leakage Currents on I-V Characteristics

Neamen Microelectronics, 4eChapter 5-16

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Effect of Collector-Base Breakdown on Common Base I-V Characteristics

Neamen Microelectronics, 4eChapter 5-17

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Effect of Collector-Base Breakdown on Common Emitter I-V Characteristics

Neamen Microelectronics, 4eChapter 5-18

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DC Equivalent Circuit for npn Common Emitter

Neamen Microelectronics, 4eChapter 5-19

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DC Equivalent Circuit for pnp Common Emitter

Neamen Microelectronics, 4eChapter 5-20

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Load Line

Neamen Microelectronics, 4eChapter 5-21

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Problem-Solving Technique:Bipolar DC Analysis

1. Assume that the transistor is biased in forward active modea. VBE = VBE(on), IB > 0, & IC = IB

2. Analyze ‘linear’ circuit.3. Evaluate the resulting state of transistor.

a. If VCE > VCE(sat), assumption is correct

b. If IB < 0, transistor likely in cutoff

c. If VCE < 0, transistor likely in saturation4. If initial assumption is incorrect, make new

assumption and return to Step 2.

Neamen Microelectronics, 4eChapter 5-22

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Voltage Transfer Characteristic for npn Circuit

Neamen Microelectronics, 4eChapter 5-23

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Voltage Transfer Characteristic for pnp Circuit

Neamen Microelectronics, 4eChapter 5-24

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Digital Logic

Inverter NOR gate

Neamen Microelectronics, 4eChapter 5-25

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Bipolar Inverter as Amplifier

Neamen Microelectronics, 4eChapter 5-26

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Effect of Improper Biasing on Amplified Signal Waveform

Neamen Microelectronics, 4eChapter 5-27

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Single Base Resistor Biasing

Neamen Microelectronics, 4eChapter 5-28

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Common Emitter with Voltage Divider Biasing and Emitter Resistor

CCTH VRRRV )/([ 212

Neamen Microelectronics, 4eChapter 5-29

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Integrated Circuit Biasing

2

1

1

I

II QC

Neamen Microelectronics, 4eChapter 5-30

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Multistage Cascade Transistor Circuit

Neamen Microelectronics, 4eChapter 5-31

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Multistage Cascode Transistor Circuit