1 Tai-Cheng Lee Spring 2006 Bipolar Junction Transistors (BJT) Tai-Cheng Lee Electrical Engineering/GIEE, NTU.

1

Tai-Cheng LeeSpring 2006

Bipolar Junction Transistors(BJT)

Tai-Cheng LeeElectrical Engineering/GIEE, NTU

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Why BJT

• Application

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Device Structure

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Operation in Active Mode-(1)

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• Profile of minority carrier concentration

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• Collector current

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• Base current

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• Emitter current

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Equivalent Circuit in Active Mode

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Structure of Actual Transistor

• Equivalent circuit model for reverse active

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Ebers-Moll (EM) Model-(1)

• Universal model for BJT

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Ebers-Moll (EM) Model-(2)

• iC –vCB characteristic of an npn transistor

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Operation of PNP Transistors

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Current-Voltage Characteristics-(1)

→

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Current-Voltage Characteristics-(2)

• Graphical representation

• Thermal effect

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Common-Base Characteristics-(1)

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Early Effect

• Large-signal circuit model

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Common-Emitter Characteristics –(1)

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• Saturation voltage VCEsat

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• Saturation resistance RCEsat

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• Analyze by E-M Model

• Breakdown voltage

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BJT Amplifier and Switch-(1)

• Large-Signal operation

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• Graphical analysis

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• Operation as a switch

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BJT Circuits at DC-(1)

• Example 5.4

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• Example 5.5

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• Example 5.6

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• Example 5.12

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Biasing BJT -(1)

• Fixed VBE

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Biasing BJT -(2)

• Classical discrete-circuit bias arrangement

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Biasing BJT -(3)

• Two power supplies

• Collector-to-base feedback

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Biasing BJT -(4)

• By a constant current source

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Small-Signal Operation-(1)

• BJT Amplifier

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• Collector current and transconductance

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• Base current and the input resistance at base

• Emitter current and the input resistance at emitter

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• Voltage gain

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Small-Signal Models-(1)

• DC and AC signal separation

• Hybrid- model

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• T model

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• Ex 5.14

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• Perform small-signal analysis on the circuit schematic

• Early Effect

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Single-Stage BJT Amplifier-(1)

• Basic structure

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Single-Stage BJT Amplifier-(2)

• Characterizing BJT Amplifier

• Refer Table 5.5

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Common-Emitter Amplifier-(1)

• Small-signal model

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Common-Emitter Amplifier-(2)

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Common-Emitter Amplifier with Emitter Resistance-(1)


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Common-Base Amplifier -(1)


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Common-Base Amplifier -(2)

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Common-Collector Amplifier -(1)

• CC amplifier is as known as emitter follower


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• Resistance reflection rule to the base side

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• Resistance reflection rule to the emitter side

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• Thevenin equivalent circuit

• Summary and comparison

1 Tai-Cheng Lee Spring 2006 Bipolar Junction Transistors (BJT) Tai-Cheng Lee Electrical Engineering/GIEE, NTU.

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