1 electronic circuits amplifiers. 2 demostrate transistor amplification determine transistor...

1

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AMPLIFIERSAMPLIFIERS

2

• Demostrate Transistor Amplification

• Determine Transistor Biasing.

• Explain Transistor Regions - Emitter, Base, Collector.

• Explore Transistors as Switches

Objectives

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3

Amplifier Out

InGain=

In

Out

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4

N

P

NThe collector is lightly doped. C

The base is thin and is lightly doped.

B

The emitter is heavily doped. E

NPN Transistor Structure

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5

The C-B junction is reverse biased.

N

P

N

NPN Transistor Bias

C

B

E

No current flows.

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6

The B-E junction is forward biased.

N

P

N

NPN Transistor Bias

C

B

E

Current flows.

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7

When both junctionsare biased....

N

P

N

NPN Transistor Bias

C

B

E

Current flowseverywhere.

Most of the emitter carriersdiffuse through the thin base

region since they are attractedby the collector.

Note that IB is smallerthan IE or IC.

IC

IB

IE

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N

P

N C

B

E

Although IB is smallerit controls IE and IC.

IC

IB

IE

Note: when the switch opens, all

currents go to zero.

Gain is something smallcontrolling something large

(IB is small).

Electronic CircuitsElectronic Circuits

9

Amplifier Out

InGain=

In

Out

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10

The C-B junction is reverse biased.

N

P

N

NPN Transistor Bias

C

B

E

No current flows.

Electronic CircuitsElectronic Circuits

11

The B-E junction is forward biased.

N

P

N

NPN Transistor Bias

C

B

E

Current flows.

Electronic CircuitsElectronic Circuits

12

When both junctionsare biased....

N

P

N

NPN Transistor Bias

C

B

E

Current flowseverywhere.

Most of the emitter carriersdiffuse through the thin base

region since they are attractedby the collector.

Note that IB is smallerthan IE or IC.

IC

IB

IE

Electronic CircuitsElectronic Circuits

13

N

P

N C

B

E

Although IB is smallerit controls IE and IC.

IC

IB

IE

Note: when the switch opens, all

currents go to zero.

Gain is something smallcontrolling something large

(IB is small).

Electronic CircuitsElectronic Circuits

14

Transistor Structure and Bias QuizThe heaviest doping is found in the ___________ region.

emitter

The thinnest of all three regions is called the ____________.

base

The collector-base junction is ___________ biased. reverse

The base-emitter junction is ____________ biased. forward

The majority of the emitter carriers flow to the ___________. collector

Electronic CircuitsElectronic Circuits