Lec7 Bipolar Junction Transistor

Basic ELECTRONICS

(2+1)ENGR MUHAMMAD SHAKEEL AKRAM

ELECTRONICS ENGINEERING FICT, BUITEMS.

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CHAPTER 4

Bipolar junction transistor

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Structure

• Three terminals • Base (lightly doped)• Emitter (heavily doped)• Collector (Moderately doped)

• Tow PN junctions • Base emitter • Base collector

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Basic Transistor Operation

• Active region • BE forward bias • BC reverse bias

• Saturation region • BE forward bias • BC forward bias

• Active region • BE reverse bias • BC reverse bias

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Basic Transistor Operation

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Basic Transistor Operation

• Transistor current• IE = IC + IB

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Transistor Characteristics and Parameters

• DC beta• DC current gain in Common Emitter • Less than 20 to greater than 200

• DC alpha • DC current gain in common base • 0.95 to 0.99

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Example

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BJT Circuit Analysis

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BJT Circuit Analysis

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BJT Circuit Analysis

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Collector Characteristic Curve

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Example

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BJT as an Amplifier

• Linearly increasing the Amplitude• Current gain β = • As IB is very small Ic ≈ IE

VcE = Vcc – Ic Rc

𝑉𝑐𝑉𝑏Av =

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BJT as an Amplifier

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BJT as a Switch VcE = Vcc – Ic Rc

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BJT as a Switch

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